diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index f77559c4..0c1a84a1 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -1,3 +1,3 @@
# These are the set of folks who should review PRs on the azureRestUpdates branch.
-* @microsoft/azure-api-stewardship-board @Azure/api-stewardship-board
-/graph/* @microsoft/graphguidelinesapprovers
+#* @microsoft/azure-api-stewardship-board @Azure/api-stewardship-board
+/graph/ @microsoft/graphguidelinesapprovers
diff --git a/Guidelines.md b/Guidelines.md
index fbbdfa5a..71c9a69d 100644
--- a/Guidelines.md
+++ b/Guidelines.md
@@ -1,2486 +1,10 @@
> # NOTICE TO READERS
+> This document has been deprecated and has been moved to the [Microsoft REST API Guidelines deprecated](./graph/Guidelines-deprecated.md). Please refer to the notes below for the latest guidance.
>
> ## **Guidance for Azure service teams**
-> Azure service teams should use the companion documents, [Azure REST API Guidelines](./azure/Guidelines.md) and [Considerations for Service Design](./azure/ConsiderationsForServiceDesign.md), when building or modifying their services. These documents provide a refined set of guidance targeted specifically for Azure services. For more information please refer to the [README](./azure/README.md) in the Azure folder.
+> Azure service teams should use the companion documents, [Azure REST API Guidelines](./azure/Guidelines.md) and [Considerations for Service Design](./azure/ConsiderationsForServiceDesign.md), when building or modifying their services. These documents provide a refined set of guidance targeted specifically for Azure services. For more information, see the [README](./azure/README.md) in the Azure folder.
>
> ## **Guidance for Microsoft Graph service teams**
-> Graph service teams should reference the companion document, [Graph REST API Guidelines](./graph/GuidelinesGraph.md) when building or modifying their services. This document and the associated pattern catalog provides a refined set of guidance targeted specifically for Microsoft Graph services.
+> Graph service teams should reference the companion document, [Microsoft Graph REST API Guidelines](./graph/GuidelinesGraph.md) when building or modifying their services. This document and the associated pattern catalog provides a refined set of guidance targeted specifically for Microsoft Graph services.
---
-
-# Microsoft REST API Guidelines
-
-## Microsoft REST API Guidelines Working Group
-
-Name | Name | Name |
----------------------------- | -------------------------------------- | ----------------------------------------
-Dave Campbell (CTO C+E) | Rick Rashid (CTO ASG) | John Shewchuk (Technical Fellow, TED HQ)
-Mark Russinovich (CTO Azure) | Steve Lucco (Technical Fellow, DevDiv) | Murali Krishnaprasad (Azure App Plat)
-Rob Howard (ASG) | Peter Torr (OSG) | Chris Mullins (ASG)
-
-
-Document editors: John Gossman (C+E), Chris Mullins (ASG), Gareth Jones (ASG), Rob Dolin (C+E), Mark Stafford (C+E)
-
-
-# Microsoft REST API Guidelines
-
-## 1. Abstract
-The Microsoft REST API Guidelines, as a design principle, encourages application developers to have resources accessible to them via a RESTful HTTP interface.
-To provide the smoothest possible experience for developers on platforms following the Microsoft REST API Guidelines, REST APIs SHOULD follow consistent design guidelines to make using them easy and intuitive.
-
-This document establishes the guidelines Microsoft REST APIs SHOULD follow so RESTful interfaces are developed consistently.
-
-## 2. Table of contents
-
-
-- [Microsoft REST API Guidelines](#microsoft-rest-api-guidelines)
- - [Microsoft REST API Guidelines Working Group](#microsoft-rest-api-guidelines-working-group)
-- [Microsoft REST API Guidelines](#microsoft-rest-api-guidelines-1)
- - [1. Abstract](#1-abstract)
- - [2. Table of contents](#2-table-of-contents)
- - [3. Introduction](#3-introduction)
- - [3.1. Recommended reading](#31-recommended-reading)
- - [4. Interpreting the guidelines](#4-interpreting-the-guidelines)
- - [4.1. Application of the guidelines](#41-application-of-the-guidelines)
- - [4.2. Guidelines for existing services and versioning of services](#42-guidelines-for-existing-services-and-versioning-of-services)
- - [4.3. Requirements language](#43-requirements-language)
- - [4.4. License](#44-license)
- - [5. Taxonomy](#5-taxonomy)
- - [5.1. Errors](#51-errors)
- - [5.2. Faults](#52-faults)
- - [5.3. Latency](#53-latency)
- - [5.4. Time to complete](#54-time-to-complete)
- - [5.5. Long running API faults](#55-long-running-api-faults)
- - [6. Client guidance](#6-client-guidance)
- - [6.1. Ignore rule](#61-ignore-rule)
- - [6.2. Variable order rule](#62-variable-order-rule)
- - [6.3. Silent fail rule](#63-silent-fail-rule)
- - [7. Consistency fundamentals](#7-consistency-fundamentals)
- - [7.1. URL structure](#71-url-structure)
- - [7.2. URL length](#72-url-length)
- - [7.3. Canonical identifier](#73-canonical-identifier)
- - [7.4. Supported methods](#74-supported-methods)
- - [7.4.1. POST](#741-post)
- - [7.4.2. PATCH](#742-patch)
- - [7.4.3. Creating resources via PATCH (UPSERT semantics)](#743-creating-resources-via-patch-upsert-semantics)
- - [7.4.4. Options and link headers](#744-options-and-link-headers)
- - [7.5. Standard request headers](#75-standard-request-headers)
- - [7.6. Standard response headers](#76-standard-response-headers)
- - [7.7. Custom headers](#77-custom-headers)
- - [7.8. Specifying headers as query parameters](#78-specifying-headers-as-query-parameters)
- - [7.9. PII parameters](#79-pii-parameters)
- - [7.10. Response formats](#710-response-formats)
- - [7.10.1. Clients-specified response format](#7101-clients-specified-response-format)
- - [7.10.2. Error condition responses](#7102-error-condition-responses)
- - [ErrorResponse : Object](#errorresponse--object)
- - [Error : Object](#error--object)
- - [InnerError : Object](#innererror--object)
- - [Examples](#examples)
- - [7.11. HTTP Status Codes](#711-http-status-codes)
- - [7.12. Client library optional](#712-client-library-optional)
- - [8. CORS](#8-cors)
- - [8.1. Client guidance](#81-client-guidance)
- - [8.1.1. Avoiding preflight](#811-avoiding-preflight)
- - [8.2. Service guidance](#82-service-guidance)
- - [9. Collections](#9-collections)
- - [9.1. Item keys](#91-item-keys)
- - [9.2. Serialization](#92-serialization)
- - [9.3. Collection URL patterns](#93-collection-url-patterns)
- - [9.3.1. Nested collections and properties](#931-nested-collections-and-properties)
- - [9.4. Big collections](#94-big-collections)
- - [9.5. Changing collections](#95-changing-collections)
- - [9.6. Sorting collections](#96-sorting-collections)
- - [9.6.1. Interpreting a sorting expression](#961-interpreting-a-sorting-expression)
- - [9.7. Filtering](#97-filtering)
- - [9.7.1. Filter operations](#971-filter-operations)
- - [9.7.2. Operator examples](#972-operator-examples)
- - [9.7.3. Operator precedence](#973-operator-precedence)
- - [9.8. Pagination](#98-pagination)
- - [9.8.1. Continuation tokens](#981-continuation-tokens)
- - [9.8.2. Server-driven paging](#982-server-driven-paging)
- - [9.8.3. Client-driven paging](#983-client-driven-paging)
- - [9.8.4. Additional considerations](#984-additional-considerations)
- - [9.9. Compound collection operations](#99-compound-collection-operations)
- - [9.10. Empty Results](#910-empty-results)
- - [10. Delta queries](#10-delta-queries)
- - [10.1. Delta links](#101-delta-links)
- - [10.2. Entity representation](#102-entity-representation)
- - [10.3. Obtaining a delta link](#103-obtaining-a-delta-link)
- - [10.4. Contents of a delta link response](#104-contents-of-a-delta-link-response)
- - [10.5. Using a delta link](#105-using-a-delta-link)
- - [11. JSON standardizations](#11-json-standardizations)
- - [11.1. JSON formatting standardization for primitive types](#111-json-formatting-standardization-for-primitive-types)
- - [11.2. Guidelines for dates and times](#112-guidelines-for-dates-and-times)
- - [11.2.1. Producing dates](#1121-producing-dates)
- - [11.2.2. Consuming dates](#1122-consuming-dates)
- - [11.2.3. Compatibility](#1123-compatibility)
- - [11.3. JSON serialization of dates and times](#113-json-serialization-of-dates-and-times)
- - [11.3.1. The `DateLiteral` format](#1131-the-dateliteral-format)
- - [11.3.2. Commentary on date formatting](#1132-commentary-on-date-formatting)
- - [11.4. Durations](#114-durations)
- - [11.5. Intervals](#115-intervals)
- - [11.6. Repeating intervals](#116-repeating-intervals)
- - [12. Versioning](#12-versioning)
- - [12.1. Versioning formats](#121-versioning-formats)
- - [12.1.1. Group versioning](#1211-group-versioning)
- - [Examples of group versioning](#examples-of-group-versioning)
- - [12.2. When to version](#122-when-to-version)
- - [12.3. Definition of a breaking change](#123-definition-of-a-breaking-change)
- - [13. Long running operations](#13-long-running-operations)
- - [13.1. Resource based long running operations (RELO)](#131-resource-based-long-running-operations-relo)
- - [13.2. Stepwise long running operations](#132-stepwise-long-running-operations)
- - [13.2.1. PUT](#1321-put)
- - [13.2.2. POST](#1322-post)
- - [13.2.3. POST, hybrid model](#1323-post-hybrid-model)
- - [13.2.4. Operations resource](#1324-operations-resource)
- - [13.2.5. Operation resource](#1325-operation-resource)
- - [Percent complete](#percent-complete)
- - [Target resource location](#target-resource-location)
- - [13.2.6. Operation tombstones](#1326-operation-tombstones)
- - [13.2.7. The typical flow, polling](#1327-the-typical-flow-polling)
- - [Example of the typical flow, polling](#example-of-the-typical-flow-polling)
- - [13.2.8. The typical flow, push notifications](#1328-the-typical-flow-push-notifications)
- - [Example of the typical flow, push notifications existing subscription](#example-of-the-typical-flow-push-notifications-existing-subscription)
- - [13.2.9. Retry-After](#1329-retry-after)
- - [13.3. Retention policy for operation results](#133-retention-policy-for-operation-results)
- - [14. Throttling, Quotas, and Limits](#14-throttling-quotas-and-limits)
- - [14.1. Principles](#141-principles)
- - [14.2. Return Codes (429 vs 503)](#142-return-codes-429-vs-503)
- - [14.3. Retry-After and RateLimit Headers](#143-retry-after-and-ratelimit-headers)
- - [14.4. Service Guidance](#144-service-guidance)
- - [14.4.1. Responsiveness](#1441-responsiveness)
- - [14.4.2. Rate Limits and Quotas](#1442-rate-limits-and-quotas)
- - [14.4.3. Overloaded services](#1443-overloaded-services)
- - [14.4.4. Example Response](#1444-example-response)
- - [14.5. Caller Guidance](#145-caller-guidance)
- - [14.6. Handling callers that ignore Retry-After headers](#146-handling-callers-that-ignore-retry-after-headers)
- - [15. Push notifications via webhooks](#15-push-notifications-via-webhooks)
- - [15.1. Scope](#151-scope)
- - [15.2. Principles](#152-principles)
- - [15.3. Types of subscriptions](#153-types-of-subscriptions)
- - [15.4. Call sequences](#154-call-sequences)
- - [15.5. Verifying subscriptions](#155-verifying-subscriptions)
- - [15.6. Receiving notifications](#156-receiving-notifications)
- - [15.6.1. Notification payload](#1561-notification-payload)
- - [15.7. Managing subscriptions programmatically](#157-managing-subscriptions-programmatically)
- - [15.7.1. Creating subscriptions](#1571-creating-subscriptions)
- - [15.7.2. Updating subscriptions](#1572-updating-subscriptions)
- - [15.7.3. Deleting subscriptions](#1573-deleting-subscriptions)
- - [15.7.4. Enumerating subscriptions](#1574-enumerating-subscriptions)
- - [15.8. Security](#158-security)
- - [16. Unsupported requests](#16-unsupported-requests)
- - [16.1. Essential guidance](#161-essential-guidance)
- - [16.2. Feature allow list](#162-feature-allow-list)
- - [16.2.1. Error response](#1621-error-response)
- - [17. Naming guidelines](#17-naming-guidelines)
- - [17.1. Approach](#171-approach)
- - [17.2. Casing](#172-casing)
- - [17.3. Names to avoid](#173-names-to-avoid)
- - [17.4. Forming compound names](#174-forming-compound-names)
- - [17.5. Identity properties](#175-identity-properties)
- - [17.6. Date and time properties](#176-date-and-time-properties)
- - [17.7. Name properties](#177-name-properties)
- - [17.8. Collections and counts](#178-collections-and-counts)
- - [17.9. Common property names](#179-common-property-names)
- - [18. Appendix](#18-appendix)
- - [18.1. Sequence diagram notes](#181-sequence-diagram-notes)
- - [18.1.1. Push notifications, per user flow](#1811-push-notifications-per-user-flow)
- - [18.1.2. Push notifications, firehose flow](#1812-push-notifications-firehose-flow)
-
-
-
-## 3. Introduction
-Developers access most Microsoft Cloud Platform resources via HTTP interfaces.
-Although each service typically provides language-specific frameworks to wrap their APIs, all of their operations eventually boil down to HTTP requests.
-Microsoft must support a wide range of clients and services and cannot rely on rich frameworks being available for every development environment.
-Thus, a goal of these guidelines is to ensure Microsoft REST APIs can be easily and consistently consumed by any client with basic HTTP support.
-
-To provide the smoothest possible experience for developers, it's important to have these APIs follow consistent design guidelines, thus making using them easy and intuitive.
-This document establishes the guidelines to be followed by Microsoft REST API developers for developing such APIs consistently.
-
-The benefits of consistency accrue in aggregate as well; consistency allows teams to leverage common code, patterns, documentation and design decisions.
-
-These guidelines aim to achieve the following:
-- Define consistent practices and patterns for all API endpoints across Microsoft.
-- Adhere as closely as possible to accepted REST/HTTP best practices in the industry at-large. [\*]
-- Make accessing Microsoft Services via REST interfaces easy for all application developers.
-- Allow service developers to leverage the prior work of other services to implement, test and document REST endpoints defined consistently.
-- Allow for partners (e.g., non-Microsoft entities) to use these guidelines for their own REST endpoint design.
-
-[\*] Note: The guidelines are designed to align with building services which comply with the REST architectural style, though they do not address or require building services that follow the REST constraints.
-The term "REST" is used throughout this document to mean services that are in the spirit of REST rather than adhering to REST by the book.*
-
-### 3.1. Recommended reading
-Understanding the philosophy behind the REST Architectural Style is recommended for developing good HTTP-based services.
-If you are new to RESTful design, here are some good resources:
-
-[REST on Wikipedia][rest-on-wikipedia] -- Overview of common definitions and core ideas behind REST.
-
-[REST Dissertation][fielding] -- The chapter on REST in Roy Fielding's dissertation on Network Architecture, "Architectural Styles and the Design of Network-based Software Architectures"
-
-[RFC 7231][rfc-7231] -- Defines the specification for HTTP/1.1 semantics, and is considered the authoritative resource.
-
-[REST in Practice][rest-in-practice] -- Book on the fundamentals of REST.
-
-## 4. Interpreting the guidelines
-### 4.1. Application of the guidelines
-These guidelines are applicable to any REST API exposed publicly by Microsoft or any partner service.
-Private or internal APIs SHOULD also try to follow these guidelines because internal services tend to eventually be exposed publicly.
- Consistency is valuable to not only external customers but also internal service consumers, and these guidelines offer best practices useful for any service.
-
-There are legitimate reasons for exemption from these guidelines.
-Obviously, a REST service that implements or must interoperate with some externally defined REST API must be compatible with that API and not necessarily these guidelines.
-Some services MAY also have special performance needs that require a different format, such as a binary protocol.
-
-### 4.2. Guidelines for existing services and versioning of services
-We do not recommend making a breaking change to a service that predates these guidelines simply for the sake of compliance.
-The service SHOULD try to become compliant at the next version release when compatibility is being broken anyway.
-When a service adds a new API, that API SHOULD be consistent with the other APIs of the same version.
-So if a service was written against version 1.0 of the guidelines, new APIs added incrementally to the service SHOULD also follow version 1.0. The service can then upgrade to align with the latest version of the guidelines at the service's next major release.
-
-### 4.3. Requirements language
-The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119][rfc-2119].
-
-### 4.4. License
-
-This work is licensed under the Creative Commons Attribution 4.0 International License.
-To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.
-
-## 5. Taxonomy
-As part of onboarding to Microsoft REST API Guidelines, services MUST comply with the taxonomy defined below.
-
-### 5.1. Errors
-Errors, or more specifically Service Errors, are defined as a client passing invalid data to the service and the service _correctly_ rejecting that data.
-Examples include invalid credentials, incorrect parameters, unknown version IDs, or similar.
-These are generally "4xx" HTTP error codes and are the result of a client passing incorrect or invalid data.
-
-Errors do _not_ contribute to overall API availability.
-
-### 5.2. Faults
-Faults, or more specifically Service Faults, are defined as the service failing to correctly return in response to a valid client request.
-These are generally "5xx" HTTP error codes.
-
-Faults _do_ contribute to the overall API availability.
-
-Calls that fail due to rate limiting or quota failures MUST NOT count as faults.
-Calls that fail as the result of a service fast-failing requests (often for its own protection) do count as faults.
-
-### 5.3. Latency
-Latency is defined as how long a particular API call takes to complete, measured as closely to the client as possible.
-This metric applies to both synchronous and asynchronous APIs in the same way.
-For long running calls, the latency is measured on the initial request and measures how long that call (not the overall operation) takes to complete.
-
-### 5.4. Time to complete
-Services that expose long operations MUST track "Time to Complete" metrics around those operations.
-
-### 5.5. Long running API faults
-For a Long Running API, it's possible for both the initial request which begins the operation and the request which retrieves the results to technically work (each passing back a 200) but for the underlying operation to have failed.
-Long Running faults MUST roll up as faults into the overall Availability metrics.
-
-## 6. Client guidance
-To ensure the best possible experience for clients talking to a REST service, clients SHOULD adhere to the following best practices:
-
-### 6.1. Ignore rule
-For loosely coupled clients where the exact shape of the data is not known before the call, if the server returns something the client wasn't expecting, the client MUST safely ignore it.
-
-Some services MAY add fields to responses without changing versions numbers.
-Services that do so MUST make this clear in their documentation and clients MUST ignore unknown fields.
-
-### 6.2. Variable order rule
-Clients MUST NOT rely on the order in which data appears in JSON service responses.
-For example, clients SHOULD be resilient to the reordering of fields within a JSON object.
-When supported by the service, clients MAY request that data be returned in a specific order.
-For example, services MAY support the use of the _$orderBy_ querystring parameter to specify the order of elements within a JSON array.
-Services MAY also explicitly specify the ordering of some elements as part of the service contract.
-For example, a service MAY always return a JSON object's "type" information as the first field in an object to simplify response parsing on the client.
-Clients MAY rely on ordering behavior explicitly identified by the service.
-
-### 6.3. Silent fail rule
-Clients requesting OPTIONAL server functionality (such as optional headers) MUST be resilient to the server ignoring that particular functionality.
-
-## 7. Consistency fundamentals
-### 7.1. URL structure
-Humans SHOULD be able to easily read and construct URLs.
-
-This facilitates discovery and eases adoption on platforms without a well-supported client library.
-
-An example of a well-structured URL is:
-
-```
-https://api.contoso.com/v1.0/people/jdoe@contoso.com/inbox
-```
-
-An example URL that is not friendly is:
-
-```
-https://api.contoso.com/EWS/OData/Users('jdoe@microsoft.com')/Folders('AAMkADdiYzI1MjUzLTk4MjQtNDQ1Yy05YjJkLWNlMzMzYmIzNTY0MwAuAAAAAACzMsPHYH6HQoSwfdpDx-2bAQCXhUk6PC1dS7AERFluCgBfAAABo58UAAA=')
-```
-
-A frequent pattern that comes up is the use of URLs as values.
-Services MAY use URLs as values.
-For example, the following is acceptable:
-
-```
-https://api.contoso.com/v1.0/items?url=https://resources.contoso.com/shoes/fancy
-```
-
-### 7.2. URL length
-The HTTP 1.1 message format, defined in RFC 7230, in section [3.1.1][rfc-7230-3-1-1], defines no length limit on the Request Line, which includes the target URL.
-From the RFC:
-
-> HTTP does not place a predefined limit on the length of a
- request-line. [...] A server that receives a request-target longer than any URI it wishes to parse MUST respond
- with a 414 (URI Too Long) status code.
-
-Services that can generate URLs longer than 2,083 characters MUST make accommodations for the clients they wish to support.
-Here are some sources for determining what target clients support:
-
- * [https://stackoverflow.com/a/417184](https://stackoverflow.com/a/417184)
- * [https://blogs.msdn.microsoft.com/ieinternals/2014/08/13/url-length-limits/](https://blogs.msdn.microsoft.com/ieinternals/2014/08/13/url-length-limits/)
-
-Also note that some technology stacks have hard and adjustable URL limits, so keep this in mind as you design your services.
-
-### 7.3. Canonical identifier
-In addition to friendly URLs, resources that can be moved or be renamed SHOULD expose a URL that contains a unique stable identifier.
-It MAY be necessary to interact with the service to obtain a stable URL from the friendly name for the resource, as in the case of the "/my" shortcut used by some services.
-
-The stable identifier is not required to be a GUID.
-
-An example of a URL containing a canonical identifier is:
-
-```
-https://api.contoso.com/v1.0/people/7011042402/inbox
-```
-
-### 7.4. Supported methods
-Operations MUST use the proper HTTP methods whenever possible, and operation idempotency MUST be respected.
-HTTP methods are frequently referred to as the HTTP verbs.
-The terms are synonymous in this context, however the HTTP specification uses the term method.
-
-Below is a list of methods that Microsoft REST services SHOULD support.
-Not all resources will support all methods, but all resources using the methods below MUST conform to their usage.
-
-Method | Description | Is Idempotent
-------- | -------------------------------------------------------------------------------------------------------------------------- | -------------
-GET | Return the current value of an object | True
-PUT | Replace an object, or create a named object, when applicable | True
-DELETE | Delete an object | True
-POST | Create a new object based on the data provided, or submit a command | False
-HEAD | Return metadata of an object for a GET response. Resources that support the GET method MAY support the HEAD method as well | True
-PATCH | Apply a partial update to an object | False
-OPTIONS | Get information about a request; see below for details. | True
-
-Table 1
-
-#### 7.4.1. POST
-POST operations SHOULD support the Location response header to specify the location of any created resource that was not explicitly named, via the Location header.
-
-As an example, imagine a service that allows creation of hosted servers, which will be named by the service:
-
-```http
-POST http://api.contoso.com/account1/servers
-```
-
-The response would be something like:
-
-```http
-201 Created
-Location: http://api.contoso.com/account1/servers/server321
-```
-
-Where "server321" is the service-allocated server name.
-
-Services MAY also return the full metadata for the created item in the response.
-
-#### 7.4.2. PATCH
-PATCH has been standardized by IETF as the method to be used for updating an existing object incrementally (see [RFC 5789][rfc-5789]).
-Microsoft REST API Guidelines compliant APIs SHOULD support PATCH.
-
-#### 7.4.3. Creating resources via PATCH (UPSERT semantics)
-Services that allow callers to specify key values on create SHOULD support UPSERT semantics, and those that do MUST support creating resources using PATCH.
-Because PUT is defined as a complete replacement of the content, it is dangerous for clients to use PUT to modify data.
-Clients that do not understand (and hence ignore) properties on a resource are not likely to provide them on a PUT when trying to update a resource, hence such properties could be inadvertently removed.
-Services MAY optionally support PUT to update existing resources, but if they do they MUST use replacement semantics (that is, after the PUT, the resource's properties MUST match what was provided in the request, including deleting any server properties that were not provided).
-
-Under UPSERT semantics, a PATCH call to a nonexistent resource is handled by the server as a "create", and a PATCH call to an existing resource is handled as an "update". To ensure that an update request is not treated as a create or vice versa, the client MAY specify precondition HTTP headers in the request.
-The service MUST NOT treat a PATCH request as an insert if it contains an If-Match header and MUST NOT treat a PATCH request as an update if it contains an If-None-Match header with a value of "*".
-
-If a service does not support UPSERT, then a PATCH call against a resource that does not exist MUST result in an HTTP "409 Conflict" error.
-
-#### 7.4.4. Options and link headers
-OPTIONS allows a client to retrieve information about a resource, at a minimum by returning the Allow header denoting the valid methods for this resource.
-
-In addition, services SHOULD include a Link header (see [RFC 5988][rfc-5988]) to point to documentation for the resource in question:
-
-```http
-Link: <{help}>; rel="help"
-```
-
-Where {help} is the URL to a documentation resource.
-
-For examples on use of OPTIONS, see [preflighting CORS cross-domain calls][cors-preflight].
-
-### 7.5. Standard request headers
-The table of request headers below SHOULD be used by Microsoft REST API Guidelines services.
-Using these headers is not mandated, but if used they MUST be used consistently.
-
-All header values MUST follow the syntax rules set forth in the specification where the header field is defined.
-Many HTTP headers are defined in [RFC7231][rfc-7231], however a complete list of approved headers can be found in the [IANA Header Registry][IANA-headers]."
-
-Header | Type | Description
---------------------------------- | ------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-Authorization | String | Authorization header for the request
-Date | Date | Timestamp of the request, based on the client's clock, in [RFC 5322][rfc-5322-3-3] date and time format. The server SHOULD NOT make any assumptions about the accuracy of the client's clock. This header MAY be included in the request, but MUST be in this format when supplied. Greenwich Mean Time (GMT) MUST be used as the time zone reference for this header when it is provided. For example: `Wed, 24 Aug 2016 18:41:30 GMT`. Note that GMT is exactly equal to UTC (Coordinated Universal Time) for this purpose.
-Accept | Content type | The requested content type for the response such as:
application/xml
text/xml
application/json
text/javascript (for JSONP)
Per the HTTP guidelines, this is just a hint and responses MAY have a different content type, such as a blob fetch where a successful response will just be the blob stream as the payload. For services following OData, the preference order specified in OData SHOULD be followed.
-Accept-Encoding | Gzip, deflate | REST endpoints SHOULD support GZIP and DEFLATE encoding, when applicable. For very large resources, services MAY ignore and return uncompressed data.
-Accept-Language | "en", "es", etc. | Specifies the preferred language for the response. Services are not required to support this, but if a service supports localization it MUST do so through the Accept-Language header.
-Accept-Charset | Charset type like "UTF-8" | Default is UTF-8, but services SHOULD be able to handle ISO-8859-1.
-Content-Type | Content type | Mime type of request body (PUT/POST/PATCH)
-Prefer | return=minimal, return=representation | If the return=minimal preference is specified, services SHOULD return an empty body in response to a successful insert or update. If return=representation is specified, services SHOULD return the created or updated resource in the response. Services SHOULD support this header if they have scenarios where clients would sometimes benefit from responses, but sometimes the response would impose too much of a hit on bandwidth.
-If-Match, If-None-Match, If-Range | String | Services that support updates to resources using optimistic concurrency control MUST support the If-Match header to do so. Services MAY also use other headers related to ETags as long as they follow the HTTP specification.
-
-### 7.6. Standard response headers
-Services SHOULD return the following response headers, except where noted in the "required" column.
-
-Response Header | Required | Description
------------------- | --------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-Date | All responses | Timestamp the response was processed, based on the server's clock, in [RFC 5322][rfc-5322-3-3] date and time format. This header MUST be included in the response. Greenwich Mean Time (GMT) MUST be used as the time zone reference for this header. For example: `Wed, 24 Aug 2016 18:41:30 GMT`. Note that GMT is exactly equal to UTC (Coordinated Universal Time) for this purpose.
-Content-Type | All responses | The content type
-Content-Encoding | All responses | GZIP or DEFLATE, as appropriate
-Preference-Applied | When specified in request | Whether a preference indicated in the Prefer request header was applied
-ETag | When the requested resource has an entity tag | The ETag response-header field provides the current value of the entity tag for the requested variant. Used with If-Match, If-None-Match and If-Range to implement optimistic concurrency control.
-
-### 7.7. Custom headers
-Custom headers MUST NOT be required for the basic operation of a given API.
-
-Some of the guidelines in this document prescribe the use of nonstandard HTTP headers.
-In addition, some services MAY need to add extra functionality, which is exposed via HTTP headers.
-The following guidelines help maintain consistency across usage of custom headers.
-
-Headers that are not standard HTTP headers MUST have one of two formats:
-
-1. A generic format for headers that are registered as "provisional" with IANA ([RFC 3864][rfc-3864])
-2. A scoped format for headers that are too usage-specific for registration
-
-These two formats are described below.
-
-### 7.8. Specifying headers as query parameters
-Some headers pose challenges for some scenarios such as AJAX clients, especially when making cross-domain calls where adding headers MAY not be supported.
-As such, some headers MAY be accepted as Query Parameters in addition to headers, with the same naming as the header:
-
-Not all headers make sense as query parameters, including most standard HTTP headers.
-
-The criteria for considering when to accept headers as parameters are:
-
-1. Any custom headers MUST be also accepted as parameters.
-2. Required standard headers MAY be accepted as parameters.
-3. Required headers with security sensitivity (e.g., Authorization header) MIGHT NOT be appropriate as parameters; the service owner SHOULD evaluate these on a case-by-case basis.
-
-The one exception to this rule is the Accept header.
-It's common practice to use a scheme with simple names instead of the full functionality described in the HTTP specification for Accept.
-
-### 7.9. PII parameters
-Consistent with their organization's privacy policy, clients SHOULD NOT transmit personally identifiable information (PII) parameters in the URL (as part of path or query string) because this information can be inadvertently exposed via client, network, and server logs and other mechanisms.
-
-Consequently, a service SHOULD accept PII parameters transmitted as headers.
-
-However, there are many scenarios where the above recommendations cannot be followed due to client or software limitations.
-To address these limitations, services SHOULD also accept these PII parameters as part of the URL consistent with the rest of these guidelines.
-
-Services that accept PII parameters -- whether in the URL or as headers -- SHOULD be compliant with privacy policy specified by their organization's engineering leadership.
-This will typically include recommending that clients prefer headers for transmission and implementations adhere to special precautions to ensure that logs and other service data collection are properly handled.
-
-### 7.10. Response formats
-For organizations to have a successful platform, they must serve data in formats developers are accustomed to using, and in consistent ways that allow developers to handle responses with common code.
-
-Web-based communication, especially when a mobile or other low-bandwidth client is involved, has moved quickly in the direction of JSON for a variety of reasons, including its tendency to be lighter weight and its ease of consumption with JavaScript-based clients.
-
-JSON property names SHOULD be camelCased.
-
-Services SHOULD provide JSON as the default encoding.
-
-#### 7.10.1. Clients-specified response format
-In HTTP, response format SHOULD be requested by the client using the Accept header.
-This is a hint, and the server MAY ignore it if it chooses to, even if this isn't typical of well-behaved servers.
-Clients MAY send multiple Accept headers and the service MAY choose one of them.
-
-The default response format (no Accept header provided) SHOULD be application/json, and all services MUST support application/json.
-
-Accept Header | Response type | Notes
----------------- | ---------------------------------- | -------------------------------------------
-application/json | Payload SHOULD be returned as JSON | Also accept text/javascript for JSONP cases
-
-```http
-GET https://api.contoso.com/v1.0/products/user
-Accept: application/json
-```
-
-#### 7.10.2. Error condition responses
-For non-success conditions, developers SHOULD be able to write one piece of code that handles errors consistently across different Microsoft REST API Guidelines services.
-This allows building of simple and reliable infrastructure to handle exceptions as a separate flow from successful responses.
-The following is based on the OData v4 JSON spec.
-However, it is very generic and does not require specific OData constructs.
-APIs SHOULD use this format even if they are not using other OData constructs.
-
-The error response MUST be a single JSON object.
-This object MUST have a name/value pair named "error". The value MUST be a JSON object.
-
-This object MUST contain name/value pairs with the names "code" and "message", and it MAY contain name/value pairs with the names "target", "details" and "innererror."
-
-The value for the "code" name/value pair is a language-independent string.
-Its value is a service-defined error code that SHOULD be human-readable.
-This code serves as a more specific indicator of the error than the HTTP error code specified in the response.
-Services SHOULD have a relatively small number (about 20) of possible values for "code", and all clients MUST be capable of handling all of them.
-Most services will require a much larger number of more specific error codes, which are not interesting to all clients.
-These error codes SHOULD be exposed in the "innererror" name/value pair as described below.
-Introducing a new value for "code" that is visible to existing clients is a breaking change and requires a version increase.
-Services can avoid breaking changes by adding new error codes to "innererror" instead.
-
-The value for the "message" name/value pair MUST be a human-readable representation of the error.
-It is intended as an aid to developers and is not suitable for exposure to end users.
-Services wanting to expose a suitable message for end users MUST do so through an [annotation][odata-json-annotations] or custom property.
-Services SHOULD NOT localize "message" for the end user, because doing so might make the value unreadable to the app developer who may be logging the value, as well as make the value less searchable on the Internet.
-
-The value for the "target" name/value pair is the target of the particular error (e.g., the name of the property in error).
-
-The value for the "details" name/value pair MUST be an array of JSON objects that MUST contain name/value pairs for "code" and "message", and MAY contain a name/value pair for "target", as described above.
-The objects in the "details" array usually represent distinct, related errors that occurred during the request.
-See example below.
-
-The value for the "innererror" name/value pair MUST be an object.
-The contents of this object are service-defined.
-Services wanting to return more specific errors than the root-level code MUST do so by including a name/value pair for "code" and a nested "innererror". Each nested "innererror" object represents a higher level of detail than its parent.
-When evaluating errors, clients MUST traverse through all of the nested "innererrors" and choose the deepest one that they understand.
-This scheme allows services to introduce new error codes anywhere in the hierarchy without breaking backwards compatibility, so long as old error codes still appear.
-The service MAY return different levels of depth and detail to different callers.
-For example, in development environments, the deepest "innererror" MAY contain internal information that can help debug the service.
-To guard against potential security concerns around information disclosure, services SHOULD take care not to expose too much detail unintentionally.
-Error objects MAY also include custom server-defined name/value pairs that MAY be specific to the code.
-Error types with custom server-defined properties SHOULD be declared in the service's metadata document.
-See example below.
-
-Error responses MAY contain [annotations][odata-json-annotations] in any of their JSON objects.
-
-We recommend that for any transient errors that may be retried, services SHOULD include a Retry-After HTTP header indicating the minimum number of seconds that clients SHOULD wait before attempting the operation again.
-
-##### ErrorResponse : Object
-
-Property | Type | Required | Description
--------- | ---- | -------- | -----------
-`error` | Error | ✔ | The error object.
-
-##### Error : Object
-
-Property | Type | Required | Description
--------- | ---- | -------- | -----------
-`code` | String | ✔ | One of a server-defined set of error codes.
-`message` | String | ✔ | A human-readable representation of the error.
-`target` | String | | The target of the error.
-`details` | Error[] | | An array of details about specific errors that led to this reported error.
-`innererror` | InnerError | | An object containing more specific information than the current object about the error.
-
-##### InnerError : Object
-
-Property | Type | Required | Description
--------- | ---- | -------- | -----------
-`code` | String | | A more specific error code than was provided by the containing error.
-`innererror` | InnerError | | An object containing more specific information than the current object about the error.
-
-##### Examples
-
-Example of "innererror":
-
-```json
-{
- "error": {
- "code": "BadArgument",
- "message": "Previous passwords may not be reused",
- "target": "password",
- "innererror": {
- "code": "PasswordError",
- "innererror": {
- "code": "PasswordDoesNotMeetPolicy",
- "minLength": "6",
- "maxLength": "64",
- "characterTypes": ["lowerCase","upperCase","number","symbol"],
- "minDistinctCharacterTypes": "2",
- "innererror": {
- "code": "PasswordReuseNotAllowed"
- }
- }
- }
- }
-}
-```
-
-In this example, the most basic error code is "BadArgument", but for clients that are interested, there are more specific error codes in "innererror."
-The "PasswordReuseNotAllowed" code may have been added by the service at a later date, having previously only returned "PasswordDoesNotMeetPolicy."
-Existing clients do not break when the new error code is added, but new clients MAY take advantage of it.
-The "PasswordDoesNotMeetPolicy" error also includes additional name/value pairs that allow the client to determine the server's configuration, validate the user's input programmatically, or present the server's constraints to the user within the client's own localized messaging.
-
-Example of "details":
-
-```json
-{
- "error": {
- "code": "BadArgument",
- "message": "Multiple errors in ContactInfo data",
- "target": "ContactInfo",
- "details": [
- {
- "code": "NullValue",
- "target": "PhoneNumber",
- "message": "Phone number must not be null"
- },
- {
- "code": "NullValue",
- "target": "LastName",
- "message": "Last name must not be null"
- },
- {
- "code": "MalformedValue",
- "target": "Address",
- "message": "Address is not valid"
- }
- ]
- }
-}
-```
-
-In this example there were multiple problems with the request, with each individual error listed in "details."
-
-### 7.11. HTTP Status Codes
-Standard HTTP Status Codes SHOULD be used; see the HTTP Status Code definitions for more information.
-
-### 7.12. Client library optional
-Developers MUST be able to develop on a wide variety of platforms and languages, such as Windows, macOS, Linux, C#, Python, Node.js, and Ruby.
-
-Services SHOULD be able to be accessed from simple HTTP tools such as curl without significant effort.
-
-Service developer portals SHOULD provide the equivalent of "Get Developer Token" to facilitate experimentation and curl support.
-
-## 8. CORS
-Services compliant with the Microsoft REST API Guidelines MUST support [CORS (Cross Origin Resource Sharing)][cors].
-Services SHOULD support an allowed origin of CORS * and enforce authorization through valid OAuth tokens.
-Services SHOULD NOT support user credentials with origin validation.
-There MAY be exceptions for special cases.
-
-### 8.1. Client guidance
-Web developers usually don't need to do anything special to take advantage of CORS.
-All of the handshake steps happen invisibly as part of the standard XMLHttpRequest calls they make.
-
-Many other platforms, such as .NET, have integrated support for CORS.
-
-#### 8.1.1. Avoiding preflight
-Because the CORS protocol can trigger preflight requests that add additional round trips to the server, performance-critical apps might be interested in avoiding them.
-The spirit behind CORS is to avoid preflight for any simple cross-domain requests that old non-CORS-capable browsers were able to make.
-All other requests require preflight.
-
-A request is "simple" and avoids preflight if its method is GET, HEAD or POST, and if it doesn't contain any request headers besides Accept, Accept-Language and Content-Language.
-For POST requests, the Content-Type header is also allowed, but only if its value is "application/x-www-form-urlencoded", "multipart/form-data" or "text/plain."
-For any other headers or values, a preflight request will happen.
-
-### 8.2. Service guidance
- At minimum, services MUST:
-- Understand the Origin request header that browsers send on cross-domain requests, and the Access-Control-Request-Method request header that they send on preflight OPTIONS requests that check for access.
-- If the Origin header is present in a request:
- - If the request uses the OPTIONS method and contains the Access-Control-Request-Method header, then it is a preflight request intended to probe for access before the actual request. Otherwise, it is an actual request. For preflight requests, beyond performing the steps below to add headers, services MUST perform no additional processing and MUST return a 200 OK. For non-preflight requests, the headers below are added in addition to the request's regular processing.
- - Add an Access-Control-Allow-Origin header to the response, containing the same value as the Origin request header. Note that this requires services to dynamically generate the header value. Resources that do not require cookies or any other form of [user credentials][cors-user-credentials] MAY respond with a wildcard asterisk (*) instead. Note that the wildcard is acceptable here only, and not for any of the other headers described below.
- - If the caller requires access to a response header that is not in the set of [simple response headers][cors-simple-headers] (Cache-Control, Content-Language, Content-Type, Expires, Last-Modified, Pragma), then add an Access-Control-Expose-Headers header containing the list of additional response header names the client should have access to.
- - If the request requires cookies, then add an Access-Control-Allow-Credentials header set to "true."
- - If the request was a preflight request (see first bullet), then the service MUST:
- - Add an Access-Control-Allow-Headers response header containing the list of request header names the client is permitted to use. This list need only contain headers that are not in the set of [simple request headers][cors-simple-headers] (Accept, Accept-Language, Content-Language). If there are no restrictions on headers the service accepts, the service MAY simply return the same value as the Access-Control-Request-Headers header sent by the client.
- - Add an Access-Control-Allow-Methods response header containing the list of HTTP methods the caller is permitted to use.
-
-Add an Access-Control-Max-Age pref response header containing the number of seconds for which this preflight response is valid (and hence can be avoided before subsequent actual requests). Note that while it is customary to use a large value like 2592000 (30 days), many browsers self-impose a much lower limit (e.g., five minutes).
-
-Because browser preflight response caches are notoriously weak, the additional round trip from a preflight response hurts performance.
-Services used by interactive Web clients where performance is critical SHOULD avoid patterns that cause a preflight request
-- For GET and HEAD calls, avoid requiring request headers that are not part of the simple set above. Allow them to be provided as query parameters instead.
- - The Authorization header is not part of the simple set, so the authentication token MUST be sent through the "access_token" query parameter instead, for resources requiring authentication. Note that passing authentication tokens in the URL is not recommended, because it can lead to the token getting recorded in server logs and exposed to anyone with access to those logs. Services that accept authentication tokens through the URL MUST take steps to mitigate the security risks, such as using short-lived authentication tokens, suppressing the auth token from getting logged, and controlling access to server logs.
-
-- Avoid requiring cookies. XmlHttpRequest will only send cookies on cross-domain requests if the "withCredentials" attribute is set; this also causes a preflight request.
- - Services that require cookie-based authentication MUST use a "dynamic canary" to secure all APIs that accept cookies.
-
-- For POST calls, prefer simple Content-Types in the set of ("application/x-www-form-urlencoded", "multipart/form-data", "text/plain") where applicable. Any other Content-Type will induce a preflight request.
- - Services MUST NOT contravene other API recommendations in the name of avoiding CORS preflight requests. In particular, in accordance with recommendations, most POST requests will actually require a preflight request due to the Content-Type.
- - If eliminating preflight is critical, then a service MAY support alternative mechanisms for data transfer, but the RECOMMENDED approach MUST also be supported.
-
-In addition, when appropriate services MAY support the JSONP pattern for simple, GET-only cross-domain access.
-In JSONP, services take a parameter indicating the format (_$format=json_) and a parameter indicating a callback (_$callback=someFunc_), and return a text/javascript document containing the JSON response wrapped in a function call with the indicated name.
-More on JSONP at Wikipedia: [JSONP](https://en.wikipedia.org/wiki/JSONP).
-
-## 9. Collections
-### 9.1. Item keys
-Services MAY support durable identifiers for each item in the collection, and that identifier SHOULD be represented in JSON as "id". These durable identifiers are often used as item keys.
-
-Collections that support durable identifiers MAY support delta queries.
-
-### 9.2. Serialization
-Collections are represented in JSON using standard array notation.
-
-### 9.3. Collection URL patterns
-Collections are located directly under the service root when they are top level, or as a segment under another resource when scoped to that resource.
-
-For example:
-
-```http
-GET https://api.contoso.com/v1.0/people
-```
-
-Whenever possible, services MUST support the "/" pattern.
-For example:
-
-```http
-GET https://{serviceRoot}/{collection}/{id}
-```
-
-Where:
-- {serviceRoot} – the combination of host (site URL) + the root path to the service
-- {collection} – the name of the collection, unabbreviated, pluralized
-- {id} – the value of the unique id property. When using the "/" pattern this MUST be the raw string/number/guid value with no quoting but properly escaped to fit in a URL segment.
-
-#### 9.3.1. Nested collections and properties
-Collection items MAY contain other collections.
-For example, a user collection MAY contain user resources that have multiple addresses:
-
-```http
-GET https://api.contoso.com/v1.0/people/123/addresses
-```
-
-```json
-{
- "value": [
- { "street": "1st Avenue", "city": "Seattle" },
- { "street": "124th Ave NE", "city": "Redmond" }
- ]
-}
-```
-
-### 9.4. Big collections
-As data grows, so do collections.
-Planning for pagination is important for all services.
-Therefore, when multiple pages are available, the serialization payload MUST contain the opaque URL for the next page as appropriate.
-Refer to the paging guidance for more details.
-
-Clients MUST be resilient to collection data being either paged or nonpaged for any given request.
-
-```json
-{
- "value":[
- { "id": "Item 1","price": 99.95,"sizes": null},
- { … },
- { … },
- { "id": "Item 99","price": 59.99,"sizes": null}
- ],
- "@nextLink": "{opaqueUrl}"
-}
-```
-
-### 9.5. Changing collections
-POST requests are not idempotent.
-This means that two POST requests sent to a collection resource with exactly the same payload MAY lead to multiple items being created in that collection.
-This is often the case for insert operations on items with a server-side generated id.
-
-For example, the following request:
-
-```http
-POST https://api.contoso.com/v1.0/people
-```
-
-Would lead to a response indicating the location of the new collection item:
-
-```http
-201 Created
-Location: https://api.contoso.com/v1.0/people/123
-```
-
-And once executed again, would likely lead to another resource:
-
-```http
-201 Created
-Location: https://api.contoso.com/v1.0/people/124
-```
-
-While a PUT request would require the indication of the collection item with the corresponding key instead:
-
-```http
-PUT https://api.contoso.com/v1.0/people/123
-```
-
-### 9.6. Sorting collections
-The results of a collection query MAY be sorted based on property values.
-The property is determined by the value of the _$orderBy_ query parameter.
-
-The value of the _$orderBy_ parameter contains a comma-separated list of expressions used to sort the items.
-A special case of such an expression is a property path terminating on a primitive property.
-
-The expression MAY include the suffix "asc" for ascending or "desc" for descending, separated from the property name by one or more spaces.
-If "asc" or "desc" is not specified, the service MUST order by the specified property in ascending order.
-
-NULL values MUST sort as "less than" non-NULL values.
-
-Items MUST be sorted by the result values of the first expression, and then items with the same value for the first expression are sorted by the result value of the second expression, and so on.
-The sort order is the inherent order for the type of the property.
-
-For example:
-
-```http
-GET https://api.contoso.com/v1.0/people?$orderBy=name
-```
-
-Will return all people sorted by name in ascending order.
-
-For example:
-
-```http
-GET https://api.contoso.com/v1.0/people?$orderBy=name desc
-```
-
-Will return all people sorted by name in descending order.
-
-Sub-sorts can be specified by a comma-separated list of property names with OPTIONAL direction qualifier.
-
-For example:
-
-```http
-GET https://api.contoso.com/v1.0/people?$orderBy=name desc,hireDate
-```
-
-Will return all people sorted by name in descending order and a secondary sort order of hireDate in ascending order.
-
-Sorting MUST compose with filtering such that:
-
-```http
-GET https://api.contoso.com/v1.0/people?$filter=name eq 'david'&$orderBy=hireDate
-```
-
-Will return all people whose name is David sorted in ascending order by hireDate.
-
-#### 9.6.1. Interpreting a sorting expression
-Sorting parameters MUST be consistent across pages, as both client and server-side paging is fully compatible with sorting.
-
-If a service does not support sorting by a property named in a _$orderBy_ expression, the service MUST respond with an error message as defined in the Responding to Unsupported Requests section.
-
-### 9.7. Filtering
-The _$filter_ querystring parameter allows clients to filter a collection of resources that are addressed by a request URL.
-The expression specified with _$filter_ is evaluated for each resource in the collection, and only items where the expression evaluates to true are included in the response.
-Resources for which the expression evaluates to false or to null, or which reference properties that are unavailable due to permissions, are omitted from the response.
-
-Example: return all Products whose Price is less than $10.00
-
-```http
-GET https://api.contoso.com/v1.0/products?$filter=price lt 10.00
-```
-
-The value of the _$filter_ option is a Boolean expression.
-
-#### 9.7.1. Filter operations
-Services that support _$filter_ SHOULD support the following minimal set of operations.
-
-Operator | Description | Example
--------------------- | --------------------- | -----------------------------------------------------
-Comparison Operators | |
-eq | Equal | city eq 'Redmond'
-ne | Not equal | city ne 'London'
-gt | Greater than | price gt 20
-ge | Greater than or equal | price ge 10
-lt | Less than | price lt 20
-le | Less than or equal | price le 100
-Logical Operators | |
-and | Logical and | price le 200 and price gt 3.5
-or | Logical or | price le 3.5 or price gt 200
-not | Logical negation | not price le 3.5
-Grouping Operators | |
-( ) | Precedence grouping | (priority eq 1 or city eq 'Redmond') and price gt 100
-
-#### 9.7.2. Operator examples
-The following examples illustrate the use and semantics of each of the logical operators.
-
-Example: all products with a name equal to 'Milk'
-
-```http
-GET https://api.contoso.com/v1.0/products?$filter=name eq 'Milk'
-```
-
-Example: all products with a name not equal to 'Milk'
-
-```http
-GET https://api.contoso.com/v1.0/products?$filter=name ne 'Milk'
-```
-
-Example: all products with the name 'Milk' that also have a price less than 2.55:
-
-```http
-GET https://api.contoso.com/v1.0/products?$filter=name eq 'Milk' and price lt 2.55
-```
-
-Example: all products that either have the name 'Milk' or have a price less than 2.55:
-
-```http
-GET https://api.contoso.com/v1.0/products?$filter=name eq 'Milk' or price lt 2.55
-```
-
-Example: all products that have the name 'Milk' or 'Eggs' and have a price less than 2.55:
-
-```http
-GET https://api.contoso.com/v1.0/products?$filter=(name eq 'Milk' or name eq 'Eggs') and price lt 2.55
-```
-
-#### 9.7.3. Operator precedence
-Services MUST use the following operator precedence for supported operators when evaluating _$filter_ expressions.
-Operators are listed by category in order of precedence from highest to lowest.
-Operators in the same category have equal precedence:
-
-| Group | Operator | Description |
-|:----------------|:---------|:----------------------|
-| Grouping | ( ) | Precedence grouping |
-| Unary | not | Logical Negation |
-| Relational | gt | Greater Than |
-| | ge | Greater than or Equal |
-| | lt | Less Than |
-| | le | Less than or Equal |
-| Equality | eq | Equal |
-| | ne | Not Equal |
-| Conditional AND | and | Logical And |
-| Conditional OR | or | Logical Or |
-
-### 9.8. Pagination
-RESTful APIs that return collections MAY return partial sets.
-Consumers of these services MUST expect partial result sets and correctly page through to retrieve an entire set.
-
-There are two forms of pagination that MAY be supported by RESTful APIs.
-Server-driven paging mitigates against denial-of-service attacks by forcibly paginating a request over multiple response payloads.
-Client-driven paging enables clients to request only the number of resources that it can use at a given time.
-
-Sorting and Filtering parameters MUST be consistent across pages, because both client- and server-side paging is fully compatible with both filtering and sorting.
-
-#### 9.8.1. Continuation tokens
-
-Paginated responses MUST indicate a partial result by including a continuation token in the response using the OData control information `@nextLink`.
-The absence of a continuation token means that no additional pages are available.
-
-Clients MUST treat the continuation URL as opaque, which means that query options may not be changed while iterating over a set of partial results.
-
-Example:
-
-```http
-GET http://api.contoso.com/v1.0/people HTTP/1.1
-Accept: application/json
-
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- ...,
- "value": [...],
- "@nextLink": "{opaqueUrl}"
-}
-```
-
-The `@nextLink` MAY be populated using either server-driven paging or client-driven paging (`@nextLink`s generated using client-driven paging should not include the `$top` query parameter).
-
-#### 9.8.2. Server-driven paging
-
-The server MAY provide server-driven paging by populating the continuation token with a `$skiptoken` query parameter.
-The `$skiptoken` value is opaque for clients and its structure should not be assumed.
-`$skiptoken` values SHOULD expire after some period of time decided by the server.
-
-Example:
-
-```http
-GET http://api.contoso.com/v1.0/people HTTP/1.1
-Accept: application/json
-
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- ...,
- "value": [...],
- "@nextLink": "http://api.contoso.com/v1.0/people?$skiptoken={opaquetoken}"
-}
-```
-
-```http
-GET http://api.contoso.com/v1.0/people?$skiptoken={opaquetoken} HTTP/1.1
-Accept: application/json
-
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- ...,
- "value": [...],
- "@nextLink": "http://api.contoso.com/v1.0/people?$skiptoken={opaquetoken2}"
-}
-```
-
-#### 9.8.3. Client-driven paging
-Clients MAY use _$top_ and _$skip_ query parameters to specify a number of results to return and an offset into the collection.
-
-The server SHOULD honor the values specified by the client; however, clients MUST be prepared to handle responses that contain a different page size or contain a continuation token.
-
-When both _$top_ and _$skip_ are given by a client, the server SHOULD first apply _$skip_ and then _$top_ on the collection.
-
-Note: If the server can't honor _$top_ and/or _$skip_, the server MUST return an error to the client informing about it instead of just ignoring the query options.
-This will avoid the risk of the client making assumptions about the data returned.
-
-Example:
-
-```http
-GET http://api.contoso.com/v1.0/people?$top=5&$skip=2 HTTP/1.1
-Accept: application/json
-
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- ...,
- "value": [...]
-}
-```
-
-#### 9.8.4. Additional considerations
-**Stable order prerequisite:** Both forms of paging depend on the collection of items having a stable order.
-The server MUST supplement any specified order criteria with additional sorts (typically by key) to ensure that items are always ordered consistently.
-
-**Missing/repeated results:** Even if the server enforces a consistent sort order, results MAY be missing or repeated based on creation or deletion of other resources.
-Clients MUST be prepared to deal with these discrepancies.
-The server SHOULD always encode the record ID of the last read record, helping the client in the process of managing repeated/missing results.
-
-**Combining client- and server-driven paging:** Note that client-driven paging does not preclude server-driven paging.
-If the page size requested by the client is larger than the default page size supported by the server, the expected response would be the number of results specified by the client, paginated as specified by the server paging settings.
-
-**Page Size:** Clients MAY request server-driven paging with a specific page size by specifying a _$maxpagesize_ preference.
-The server SHOULD honor this preference if the specified page size is smaller than the server's default page size.
-
-**Paginating embedded collections:** It is possible for both client-driven paging and server-driven paging to be applied to embedded collections.
-If a server paginates an embedded collection, it MUST include additional continuation tokens as appropriate.
-
-**Recordset count:** Developers who want to know the full number of records across all pages, MAY include the query parameter _$count=true_ to tell the server to include the count of items in the response.
-
-### 9.9. Compound collection operations
-Filtering, Sorting and Pagination operations MAY all be performed against a given collection.
-When these operations are performed together, the evaluation order MUST be:
-
-1. **Filtering**. This includes all range expressions performed as an AND operation.
-2. **Sorting**. The potentially filtered list is sorted according to the sort criteria.
-3. **Pagination**. The materialized paginated view is presented over the filtered, sorted list. This applies to both server-driven pagination and client-driven pagination.
-
-### 9.10. Empty Results
-When a filter is performed on a collection and the result set is empty you MUST respond with a valid response body and a 200 response code.
-In this example the filters supplied by the client resulted in a empty result set.
-The response body is returned as normal and the _value_ attribute is set to a empty collection.
-A client MAY be expecting metadata attributes like _maxItems_ based on the format of your responses to similar calls which produced results.
-You SHOULD maintain consistency in your API whenever possible.
-
-```http
-GET https://api.contoso.com/v1.0/products?$filter=(name eq 'Milk' or name eq 'Eggs') and price lt 2.55
-Accept: application/json
-
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- ...,
- "maxItems": 0,
- "value": []
-}
-```
-
-## 10. Delta queries
-Services MAY choose to support delta queries.
-
-### 10.1. Delta links
-Delta links are opaque, service-generated links that the client uses to retrieve subsequent changes to a result.
-
-At a conceptual level delta links are based on a defining query that describes the set of results for which changes are being tracked.
-The delta link encodes the collection of entities for which changes are being tracked, along with a starting point from which to track changes.
-
-If the query contains a filter, the response MUST include only changes to entities matching the specified criteria.
-The key principles of the Delta Query are:
-- Every item in the set MUST have a persistent identifier. That identifier SHOULD be represented as "id". This identifier is a service defined opaque string that MAY be used by the client to track object across calls.
-- The delta MUST contain an entry for each entity that newly matches the specified criteria, and MUST contain a "@removed" entry for each entity that no longer matches the criteria.
-- Re-evaluate the query and compare it to original set of results; every entry uniquely in the current set MUST be returned as an Add operation, and every entry uniquely in the original set MUST be returned as a "remove" operation.
-- Each entity that previously did not match the criteria but matches it now MUST be returned as an "add"; conversely, each entity that previously matched the query but no longer does MUST be returned as a "@removed" entry.
-- Entities that have changed MUST be included in the set using their standard representation.
-- Services MAY add additional metadata to the "@removed" node, such as a reason for removal, or a "removed at" timestamp. We recommend teams coordinate with the Microsoft REST API Guidelines Working Group on extensions to help maintain consistency.
-
-The delta link MUST NOT encode any client top or skip value.
-
-### 10.2. Entity representation
-Added and updated entities are represented in the entity set using their standard representation.
-From the perspective of the set, there is no difference between an added or updated entity.
-
-Removed entities are represented using only their "id" and an "@removed" node.
-The presence of an "@removed" node MUST represent the removal of the entry from the set.
-
-### 10.3. Obtaining a delta link
-A delta link is obtained by querying a collection or entity and appending a $delta query string parameter.
-For example:
-
-```http
-GET https://api.contoso.com/v1.0/people?$delta
-HTTP/1.1
-Accept: application/json
-
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- "value":[
- { "id": "1", "name": "Matt"},
- { "id": "2", "name": "Mark"},
- { "id": "3", "name": "John"}
- ],
- "@deltaLink": "{opaqueUrl}"
-}
-```
-
-Note: If the collection is paginated the deltaLink will only be present on the final page but MUST reflect any changes to the data returned across all pages.
-
-### 10.4. Contents of a delta link response
-Added/Updated entries MUST appear as regular JSON objects, with regular item properties.
-Returning the added/modified items in their regular representation allows the client to merge them into their existing "cache" using standard merge concepts based on the "id" field.
-
-Entries removed from the defined collection MUST be included in the response.
-Items removed from the set MUST be represented using only their "id" and an "@removed" node.
-
-### 10.5. Using a delta link
-The client requests changes by invoking the GET method on the delta link.
-The client MUST use the delta URL as is -- in other words the client MUST NOT modify the URL in any way (e.g., parsing it and adding additional query string parameters).
-In this example:
-
-```http
-GET https://{opaqueUrl} HTTP/1.1
-Accept: application/json
-
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- "value":[
- { "id": "1", "name": "Mat"},
- { "id": "2", "name": "Marc"},
- { "id": "3", "@removed": {} },
- { "id": "4", "name": "Luc"}
- ],
- "@deltaLink": "{opaqueUrl}"
-}
-```
-
-The results of a request against the delta link may span multiple pages but MUST be ordered by the service across all pages in such a way as to ensure a deterministic result when applied in order to the response that contained the delta link.
-
-If no changes have occurred, the response is an empty collection that contains a delta link for subsequent changes if requested.
-This delta link MAY be identical to the delta link resulting in the empty collection of changes.
-
-If the delta link is no longer valid, the service MUST respond with _410 Gone_. The response SHOULD include a Location header that the client can use to retrieve a new baseline set of results.
-
-## 11. JSON standardizations
-### 11.1. JSON formatting standardization for primitive types
-Primitive values MUST be serialized to JSON following the rules of [RFC8259][rfc-8259].
-
-**Important note for 64bit integers:** JavaScript will silently truncate integers larger than `Number.MAX_SAFE_INTEGER` (2^53-1) or numbers smaller than `Number.MIN_SAFE_INTEGER` (-2^53+1). If the service is expected to return integer values outside the range of safe values, strongly consider returning the value as a string in order to maximize interoperability and avoid data loss.
-
-### 11.2. Guidelines for dates and times
-#### 11.2.1. Producing dates
-Services MUST produce dates using the `DateLiteral` format, and SHOULD use the `Iso8601Literal` format unless there are compelling reasons to do otherwise.
-Services that do use the `StructuredDateLiteral` format MUST NOT produce dates using the `T` kind unless BOTH the additional precision is REQUIRED, and ECMAScript clients are explicitly unsupported.
-(Non-Normative statement: When deciding which particular `DateKind` to standardize on, the approximate order of preference is `E, C, U, W, O, X, I, T`.
-This optimizes for ECMAScript, .NET, and C++ programmers, in that order.)
-
-#### 11.2.2. Consuming dates
-Services MUST accept dates from clients that use the same `DateLiteral` format (including the `DateKind`, if applicable) that they produce, and SHOULD accept dates using any `DateLiteral` format.
-
-#### 11.2.3. Compatibility
-Services MUST use the same `DateLiteral` format (including the same `DateKind`, if applicable) for all resources of the same type, and SHOULD use the same `DateLiteral` format (and `DateKind`, if applicable) for all resources across the entire service.
-
-Any change to the `DateLiteral` format produced by the service (including the `DateKind`, if applicable) and any reductions in the `DateLiteral` formats (and `DateKind`, if applicable) accepted by the service MUST be treated as a breaking change.
-Any widening of the `DateLiteral` formats accepted by the service is NOT considered a breaking change.
-
-### 11.3. JSON serialization of dates and times
-Round-tripping serialized dates with JSON is a hard problem.
-Although ECMAScript supports literals for most built-in types, it does not define a literal format for dates.
-The Web has coalesced around the [ECMAScript subset of ISO 8601 date formats (ISO 8601)][iso-8601], but there are situations where this format is not desirable.
-For those cases, this document defines a JSON serialization format that can be used to unambiguously represent dates in different formats.
-Other serialization formats (such as XML) could be derived from this format.
-
-#### 11.3.1. The `DateLiteral` format
-Dates represented in JSON are serialized using the following grammar.
-Informally, a `DateValue` is either an ISO 8601-formatted string or a JSON object containing two properties named `kind` and `value` that together define a point in time.
-The following is not a context-free grammar; in particular, the interpretation of `DateValue` depends on the value of `DateKind`, but this minimizes the number of productions required to describe the format.
-
-```
-DateLiteral:
- Iso8601Literal
- StructuredDateLiteral
-
-Iso8601Literal:
- A string literal as defined in https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15. Note that the full grammar for ISO 8601 (such as "basic format" without separators) is not supported.
- All dates default to UTC unless specified otherwise.
-
-StructuredDateLiteral:
- { DateKindProperty , DateValueProperty }
- { DateValueProperty , DateKindProperty }
-
-DateKindProperty
- "kind" : DateKind
-
-DateKind:
- "C" ; see below
- "E" ; see below
- "I" ; see below
- "O" ; see below
- "T" ; see below
- "U" ; see below
- "W" ; see below
- "X" ; see below
-
-DateValueProperty:
- "value" : DateValue
-
-DateValue:
- UnsignedInteger ; not defined here
- SignedInteger ; not defined here
- RealNumber ; not defined here
- Iso8601Literal ; as above
-```
-
-#### 11.3.2. Commentary on date formatting
-A `DateLiteral` using the `Iso8601Literal` production is relatively straightforward.
-Here is an example of an object with a property named `creationDate` that is set to February 13, 2015, at 1:15 p.m. UTC:
-
-```json
-{ "creationDate" : "2015-02-13T13:15Z" }
-```
-
-The `StructuredDateLiteral` consists of a `DateKind` and an accompanying `DateValue` whose valid values (and their interpretation) depend on the `DateKind`. The following table describes the valid combinations and their meaning:
-
-DateKind | DateValue | Colloquial Name & Interpretation | More Info
--------- | --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------
-C | UnsignedInteger | "CLR"; number of milliseconds since midnight January 1, 0001; negative values are not allowed. *See note below.* | [MSDN][clr-time]
-E | SignedInteger | "ECMAScript"; number of milliseconds since midnight, January 1, 1970. | [ECMA International][ecmascript-time]
-I | Iso8601Literal | "ISO 8601"; a string limited to the ECMAScript subset. |
-O | RealNumber | "OLE Date"; integral part is the number of days since midnight, December 31, 1899, and fractional part is the time within the day (0.5 = midday). | [MSDN][ole-date]
-T | SignedInteger | "Ticks"; number of ticks (100-nanosecond intervals) since midnight January 1, 1601. *See note below.* | [MSDN][ticks-time]
-U | SignedInteger | "UNIX"; number of seconds since midnight, January 1, 1970. | [MSDN][unix-time]
-W | SignedInteger | "Windows"; number of milliseconds since midnight January 1, 1601. *See note below.* | [MSDN][windows-time]
-X | RealNumber | "Excel"; as for `O` but the year 1900 is incorrectly treated as a leap year, and day 0 is "January 0 (zero)". | [Microsoft Support][excel-time]
-
-**Important note for `C` and `W` kinds:** The native CLR and Windows times are represented by 100-nanosecond "tick" values.
-To interoperate with ECMAScript clients that have limited precision, _these values MUST be converted to and from milliseconds_ when (de)serialized as a `DateLiteral`.
-One millisecond is equivalent to 10,000 ticks.
-
-**Important note for `T` kind:** This kind preserves the full fidelity of the Windows native time formats (and is trivially convertible to and from the native CLR format) but is incompatible with ECMAScript clients.
-Therefore, its use SHOULD be limited to only those scenarios that both require the additional precision and do not need to interoperate with ECMAScript clients.
-
-Here is the same example of an object with a property named creationDate that is set to February 13, 2015, at 1:15 p.m. UTC, using several formats:
-
-```json
-[
- { "creationDate" : { "kind" : "O", "value" : 42048.55 } },
- { "creationDate" : { "kind" : "E", "value" : 1423862100000 } }
-]
-```
-
-One of the benefits of separating the kind from the value is that once a client knows the kind used by a particular service, it can interpret the value without requiring any additional parsing.
-In the common case of the value being a number, this makes coding easier for developers:
-
-```csharp
-// We know this service always gives out ECMAScript-format dates
-var date = new Date(serverResponse.someObject.creationDate.value);
-```
-
-### 11.4. Durations
-[Durations][wikipedia-iso8601-durations] need to be serialized in conformance with [ISO 8601][wikipedia-iso8601-durations].
-Durations are "represented by the format `P[n]Y[n]M[n]DT[n]H[n]M[n]S`."
-From the standard:
-- P is the duration designator (historically called "period") placed at the start of the duration representation.
-- Y is the year designator that follows the value for the number of years.
-- M is the month designator that follows the value for the number of months.
-- W is the week designator that follows the value for the number of weeks.
-- D is the day designator that follows the value for the number of days.
-- T is the time designator that precedes the time components of the representation.
-- H is the hour designator that follows the value for the number of hours.
-- M is the minute designator that follows the value for the number of minutes.
-- S is the second designator that follows the value for the number of seconds.
-
-For example, "P3Y6M4DT12H30M5S" represents a duration of "three years, six months, four days, twelve hours, thirty minutes, and five seconds."
-
-### 11.5. Intervals
-[Intervals][wikipedia-iso8601-intervals] are defined as part of [ISO 8601][wikipedia-iso8601-intervals].
-- Start and end, such as "2007-03-01T13:00:00Z/2008-05-11T15:30:00Z"
-- Start and duration, such as "2007-03-01T13:00:00Z/P1Y2M10DT2H30M"
-- Duration and end, such as "P1Y2M10DT2H30M/2008-05-11T15:30:00Z"
-- Duration only, such as "P1Y2M10DT2H30M", with additional context information
-
-### 11.6. Repeating intervals
-[Repeating Intervals][wikipedia-iso8601-repeatingintervals], as per [ISO 8601][wikipedia-iso8601-repeatingintervals], are:
-
-> Formed by adding "R[n]/" to the beginning of an interval expression, where R is used as the letter itself and [n] is replaced by the number of repetitions.
-Leaving out the value for [n] means an unbounded number of repetitions.
-
-For example, to repeat the interval of "P1Y2M10DT2H30M" five times starting at "2008-03-01T13:00:00Z", use "R5/2008-03-01T13:00:00Z/P1Y2M10DT2H30M."
-
-## 12. Versioning
-**All APIs compliant with the Microsoft REST API Guidelines MUST support explicit versioning.** It's critical that clients can count on services to be stable over time, and it's critical that services can add features and make changes.
-
-### 12.1. Versioning formats
-Services are versioned using a Major.Minor versioning scheme.
-Services MAY opt for a "Major" only version scheme in which case the ".0" is implied and all other rules in this section apply.
-Two options for specifying the version of a REST API request are supported:
-- Embedded in the path of the request URL, at the end of the service root: `https://api.contoso.com/v1.0/products/users`
-- As a query string parameter of the URL: `https://api.contoso.com/products/users?api-version=1.0`
-
-Guidance for choosing between the two options is as follows:
-
-1. Services co-located behind a DNS endpoint MUST use the same versioning mechanism.
-2. In this scenario, a consistent user experience across the endpoint is paramount. The Microsoft REST API Guidelines Working Group recommends that new top-level DNS endpoints are not created without explicit conversations with your organization's leadership team.
-3. Services that guarantee the stability of their REST API's URL paths, even through future versions of the API, MAY adopt the query string parameter mechanism. This means the naming and structure of the relationships described in the API cannot evolve after the API ships, even across versions with breaking changes.
-4. Services that cannot ensure URL path stability across future versions MUST embed the version in the URL path.
-
-Certain bedrock services such as Microsoft's Azure Active Directory may be exposed behind multiple endpoints.
-Such services MUST support the versioning mechanisms of each endpoint, even if that means supporting multiple versioning mechanisms.
-
-#### 12.1.1. Group versioning
-Group versioning is an OPTIONAL feature that MAY be offered on services using the query string parameter mechanism.
-Group versions allow for logical grouping of API endpoints under a common versioning moniker.
-This allows developers to look up a single version number and use it across multiple endpoints.
-Group version numbers are well known, and services SHOULD reject any unrecognized values.
-
-Internally, services will take a Group Version and map it to the appropriate Major.Minor version.
-
-The Group Version format is defined as YYYY-MM-DD, for example 2012-12-07 for December 7, 2012. This Date versioning format applies only to Group Versions and SHOULD NOT be used as an alternative to Major.Minor versioning.
-
-##### Examples of group versioning
-
-| Group | Major.Minor |
-|:-----------|:------------|
-| 2012-12-01 | 1.0 |
-| | 1.1 |
-| | 1.2 |
-| 2013-03-21 | 1.0 |
-| | 2.0 |
-| | 3.0 |
-| | 3.1 |
-| | 3.2 |
-| | 3.3 |
-
-Version Format | Example | Interpretation
------------------------------ | ---------------------- | ------------------------------------------
-{groupVersion} | 2013-03-21, 2012-12-01 | 3.3, 1.2
-{majorVersion} | 3 | 3.0
-{majorVersion}.{minorVersion} | 1.2 | 1.2
-
-Clients can specify either the group version or the Major.Minor version:
-
-For example:
-
-```http
-GET http://api.contoso.com/acct1/c1/blob2?api-version=1.0
-```
-
-```http
-PUT http://api.contoso.com/acct1/c1/b2?api-version=2011-12-07
-```
-
-### 12.2. When to version
-Services MUST increment their version number in response to any breaking API change.
-See the following section for a detailed discussion of what constitutes a breaking change.
-Services MAY increment their version number for nonbreaking changes as well, if desired.
-
-Use a new major version number to signal that support for existing clients will be deprecated in the future.
-When introducing a new major version, services MUST provide a clear upgrade path for existing clients and develop a plan for deprecation that is consistent with their business group's policies.
-Services SHOULD use a new minor version number for all other changes.
-
-Online documentation of versioned services MUST indicate the current support status of each previous API version and provide a path to the latest version.
-
-### 12.3. Definition of a breaking change
-Changes to the contract of an API are considered a breaking change.
-Changes that impact the backwards compatibility of an API are a breaking change.
-
-Teams MAY define backwards compatibility as their business needs require.
-For example, Azure defines the addition of a new JSON field in a response to be not backwards compatible.
-Office 365 has a looser definition of backwards compatibility and allows JSON fields to be added to responses.
-
-Clear examples of breaking changes:
-
-1. Removing or renaming APIs or API parameters
-2. Changes in behavior for an existing API
-3. Changes in Error Codes and Fault Contracts
-4. Anything that would violate the [Principle of Least Astonishment][principle-of-least-astonishment]
-
-Services MUST explicitly define their definition of a breaking change, especially with regard to adding new fields to JSON responses and adding new API arguments with default fields.
-Services that are co-located behind a DNS Endpoint with other services MUST be consistent in defining contract extensibility.
-
-The applicable changes described [in this section of the OData V4 spec][odata-breaking-changes] SHOULD be considered part of the minimum bar that all services MUST consider a breaking change.
-
-## 13. Long running operations
-Long running operations, sometimes called async operations, tend to mean different things to different people.
-This section sets forth guidance around different types of long running operations, and describes the wire protocols and best practices for these types of operations.
-
-1. One or more clients MUST be able to monitor and operate on the same resource at the same time.
-2. The state of the system SHOULD be discoverable and testable at all times. Clients SHOULD be able to determine the system state even if the operation tracking resource is no longer active. The act of querying the state of a long running operation should itself leverage principles of the web. i.e. well-defined resources with uniform interface semantics. Clients MAY issue a GET on some resource to determine the state of a long running operation
-3. Long running operations SHOULD work for clients looking to "Fire and Forget" and for clients looking to actively monitor and act upon results.
-4. Cancellation does not explicitly mean rollback. On a per-API defined case it may mean rollback, or compensation, or completion, or partial completion, etc. Following a cancelled operation, It SHOULD NOT be a client's responsibility to return the service to a consistent state which allows continued service.
-
-### 13.1. Resource based long running operations (RELO)
-Resource based modeling is where the status of an operation is encoded in the resource and the wire protocol used is the standard synchronous protocol.
-In this model state transitions are well defined and goal states are similarly defined.
-
-_This is the preferred model for long running operations and should be used wherever possible._ Avoiding the complexity and mechanics of the LRO Wire Protocol makes things simpler for our users and tooling chain.
-
-An example may be a machine reboot, where the operation itself completes synchronously but the GET operation on the virtual machine resource would have a "state: Rebooting", "state: Running" that could be queried at any time.
-
-This model MAY integrate Push Notifications.
-
-While most operations are likely to be POST semantics, in addition to POST semantics, services MAY support PUT semantics via routing to simplify their APIs.
-For example, a user that wants to create a database named "db1" could call:
-
-```http
-PUT https://api.contoso.com/v1.0/databases/db1
-```
-
-In this scenario the databases segment is processing the PUT operation.
-
-Services MAY also use the hybrid defined below.
-
-### 13.2. Stepwise long running operations
-A stepwise operation is one that takes a long, and often unpredictable, length of time to complete, and doesn't offer state transition modeled in the resource.
-This section outlines the approach that services should use to expose such long running operations.
-
-Service MAY expose stepwise operations.
-
-> Stepwise Long Running Operations are sometimes called "Async" operations.
-This causes confusion, as it mixes elements of platforms ("Async / await", "promises", "futures") with elements of API operation.
-This document uses the term "Stepwise Long Running Operation" or often just "Stepwise Operation" to avoid confusion over the word "Async".
-
-Services MUST perform as much synchronous validation as practical on stepwise requests.
-Services MUST prioritize returning errors in a synchronous way, with the goal of having only "Valid" operations processed using the long running operation wire protocol.
-
-For an API that's defined as a Stepwise Long Running Operation the service MUST go through the Stepwise Long Running Operation flow even if the operation can be completed immediately.
-In other words, APIs must adopt and stick with an LRO pattern and not change patterns based on circumstance.
-
-#### 13.2.1. PUT
-Services MAY enable PUT requests for entity creation.
-
-```http
-PUT https://api.contoso.com/v1.0/databases/db1
-```
-
-In this scenario the _databases_ segment is processing the PUT operation.
-
-```http
-HTTP/1.1 202 Accepted
-Operation-Location: https://api.contoso.com/v1.0/operations/123
-```
-
-For services that need to return a 201 Created here, use the hybrid flow described below.
-
-The 202 Accepted should return no body.
-The 201 Created case should return the body of the target resource.
-
-#### 13.2.2. POST
-Services MAY enable POST requests for entity creation.
-
-```http
-POST https://api.contoso.com/v1.0/databases/
-
-{
- "fileName": "someFile.db",
- "color": "red"
-}
-```
-
-```http
-HTTP/1.1 202 Accepted
-Operation-Location: https://api.contoso.com/v1.0/operations/123
-```
-
-#### 13.2.3. POST, hybrid model
-Services MAY respond synchronously to POST requests to collections that create a resource even if the resources aren't fully created when the response is generated.
-In order to use this pattern, the response MUST include a representation of the incomplete resource and an indication that it is incomplete.
-
-For example:
-
-```http
-POST https://api.contoso.com/v1.0/databases/ HTTP/1.1
-Host: api.contoso.com
-Content-Type: application/json
-Accept: application/json
-
-{
- "fileName": "someFile.db",
- "color": "red"
-}
-```
-
-Service response says the database has been created, but indicates the request is not completed by including the Operation-Location header.
-In this case the status property in the response payload also indicates the operation has not fully completed.
-
-```http
-HTTP/1.1 201 Created
-Location: https://api.contoso.com/v1.0/databases/db1
-Operation-Location: https://api.contoso.com/v1.0/operations/123
-
-{
- "databaseName": "db1",
- "color": "red",
- "Status": "Provisioning",
- [ … other fields for "database" …]
-}
-```
-
-#### 13.2.4. Operations resource
-Services MAY provide a "/operations" resource at the tenant level.
-
-Services that provide the "/operations" resource MUST provide GET semantics.
-GET MUST enumerate the set of operations, following standard pagination, sorting, and filtering semantics.
-The default sort order for this operation MUST be:
-
-Primary Sort | Secondary Sort
----------------------- | -----------------------
-Not Started Operations | Operation Creation Time
-Running Operations | Operation Creation Time
-Completed Operations | Operation Creation Time
-
-Note that "Completed Operations" is a goal state (see below), and may actually be any of several different states such as "successful", "cancelled", "failed" and so forth.
-
-#### 13.2.5. Operation resource
-An operation is a user addressable resource that tracks a stepwise long running operation.
-Operations MUST support GET semantics.
-The GET operation against an operation MUST return:
-
-1. The operation resource, it's state, and any extended state relevant to the particular API.
-2. 200 OK as the response code.
-
-Services MAY support operation cancellation by exposing DELETE on the operation.
-If supported DELETE operations MUST be idempotent.
-
-> Note: From an API design perspective, cancellation does not explicitly mean rollback.
-On a per-API defined case it may mean rollback, or compensation, or completion, or partial completion, etc.
-Following a cancelled operation, It SHOULD NOT be a client's responsibility to return the service to a consistent state which allows continued service.
-
-Services that do not support operation cancellation MUST return a 405 Method Not Allowed in the event of a DELETE.
-
-Operations MUST support the following states:
-
-1. NotStarted
-2. Running
-3. Succeeded. Terminal State.
-4. Failed. Terminal State.
-
-Services MAY add additional states, such as "Cancelled" or "Partially Completed". Services that support cancellation MUST sufficiently describe their cancellation such that the state of the system can be accurately determined, and any compensating actions may be run.
-
-Services that support additional states should consider this list of canonical names and avoid creating new names if possible: Cancelling, Cancelled, Aborting, Aborted, Tombstone, Deleting, Deleted.
-
-An operation MUST contain, and provide in the GET response, the following information:
-
-1. The timestamp when the operation was created.
-2. A timestamp for when the current state was entered.
-3. The operation state (notstarted / running / completed).
-
-Services MAY add additional, API specific, fields into the operation.
-The operation status JSON returned looks like:
-
-```json
-{
- "createdDateTime": "2015-06-19T12-01-03.45Z",
- "lastActionDateTime": "2015-06-19T12-01-03.45Z",
- "status": "notstarted | running | succeeded | failed"
-}
-```
-
-##### Percent complete
-Sometimes it is impossible for services to know with any accuracy when an operation will complete.
-Which makes using the Retry-After header problematic.
-In that case, services MAY include, in the operationStatus JSON, a percent complete field.
-
-```json
-{
- "createdDateTime": "2015-06-19T12-01-03.45Z",
- "percentComplete": "50",
- "status": "running"
-}
-```
-
-In this example the server has indicated to the client that the long running operation is 50% complete.
-
-##### Target resource location
-For operations that result in, or manipulate, a resource the service MUST include the target resource location in the status upon operation completion.
-
-```json
-{
- "createdDateTime": "2015-06-19T12-01-03.45Z",
- "lastActionDateTime": "2015-06-19T12-06-03.0024Z",
- "status": "succeeded",
- "resourceLocation": "https://api.contoso.com/v1.0/databases/db1"
-}
-```
-
-#### 13.2.6. Operation tombstones
-Services MAY choose to support tombstoned operations.
-Services MAY choose to delete tombstones after a service defined period of time.
-
-#### 13.2.7. The typical flow, polling
-- Client invokes a stepwise operation by invoking an action using POST
-- The server MUST indicate the request has been started by responding with a 202 Accepted status code. The response SHOULD include the location header containing a URL that the client should poll for the results after waiting the number of seconds specified in the Retry-After header.
-- Client polls the location until receiving a 200 response with a terminal operation state.
-
-##### Example of the typical flow, polling
-Client invokes the restart action:
-
-```http
-POST https://api.contoso.com/v1.0/databases HTTP/1.1
-Accept: application/json
-
-{
- "fromFile": "myFile.db",
- "color": "red"
-}
-```
-
-The server response indicates the request has been created.
-
-```http
-HTTP/1.1 202 Accepted
-Operation-Location: https://api.contoso.com/v1.0/operations/123
-```
-
-Client waits for a period of time then invokes another request to try to get the operation status.
-
-```http
-GET https://api.contoso.com/v1.0/operations/123
-Accept: application/json
-```
-
-Server responds that results are still not ready and optionally provides a recommendation to wait 30 seconds.
-
-```http
-HTTP/1.1 200 OK
-Retry-After: 30
-
-{
- "createdDateTime": "2015-06-19T12-01-03.4Z",
- "status": "running"
-}
-```
-
-Client waits the recommended 30 seconds and then invokes another request to get the results of the operation.
-
-```http
-GET https://api.contoso.com/v1.0/operations/123
-Accept: application/json
-```
-
-Server responds with a "status:succeeded" operation that includes the resource location.
-
-```http
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- "createdDateTime": "2015-06-19T12-01-03.45Z",
- "lastActionDateTime": "2015-06-19T12-06-03.0024Z",
- "status": "succeeded",
- "resourceLocation": "https://api.contoso.com/v1.0/databases/db1"
-}
-```
-
-#### 13.2.8. The typical flow, push notifications
-1. Client invokes a long running operation by invoking an action using POST. The client has a push notification already setup on the parent resource.
-2. The service indicates the request has been started by responding with a 202 Accepted status code. The client ignores everything else.
-3. Upon completion of the overall operation the service pushes a notification via the subscription on the parent resource.
-4. The client retrieves the operation result via the resource URL.
-
-##### Example of the typical flow, push notifications existing subscription
-Client invokes the backup action.
-The client already has a push notification subscription setup for db1.
-
-```http
-POST https://api.contoso.com/v1.0/databases/db1?backup HTTP/1.1
-Accept: application/json
-```
-
-The server response indicates the request has been accepted.
-
-```http
-HTTP/1.1 202 Accepted
-Operation-Location: https://api.contoso.com/v1.0/operations/123
-```
-
-The caller ignores all the headers in the return.
-
-The target URL receives a push notification when the operation is complete.
-
-```http
-HTTP/1.1 200 OK
-Content-Type: application/json
-
-{
- "value": [
- {
- "subscriptionId": "1234-5678-1111-2222",
- "context": "subscription context that was specified at setup",
- "resourceUrl": "https://api.contoso.com/v1.0/databases/db1",
- "userId" : "contoso.com/user@contoso.com",
- "tenantId" : "contoso.com"
- }
- ]
-}
-```
-
-#### 13.2.9. Retry-After
-In the examples above the Retry-After header indicates the number of seconds that the client should wait before trying to get the result from the URL identified by the location header.
-
-The HTTP specification allows the Retry-After header to alternatively specify a HTTP date, so clients should be prepared to handle this as well.
-
-```http
-HTTP/1.1 202 Accepted
-Operation-Location: http://api.contoso.com/v1.0/operations/123
-Retry-After: 60
-```
-
-Note: The use of the HTTP Date is inconsistent with the use of ISO 8601 Date Format used throughout this document, but is explicitly defined by the HTTP standard in [RFC 7231][rfc-7231-7-1-1-1]. Services SHOULD prefer the integer number of seconds (in decimal) format over the HTTP date format.
-
-### 13.3. Retention policy for operation results
-In some situations, the result of a long running operation is not a resource that can be addressed.
-For example, if you invoke a long running Action that returns a Boolean (rather than a resource).
-In these situations, the Location header points to a place where the Boolean result can be retrieved.
-
-Which begs the question: "How long should operation results be retained?"
-
-A recommended minimum retention time is 24 hours.
-
-Operations SHOULD transition to "tombstone" for an additional period of time prior to being purged from the system.
-
-## 14. Throttling, Quotas, and Limits
-### 14.1. Principles
-Services should be as responsive as possible, so as not to block callers.
-As a rule of thumb any API call that is expected to take longer than 0.5 seconds in the 99th percentile, should consider using the Long-running Operations pattern for those calls.
-Obviously, services cannot guarantee these response times in the face of potentially unlimited load from callers. Services should therefore design and document call request limits for clients, and respond with appropriate, actionable errors and error messages if these limits are exceeded.
-Services should respond quickly with an error when they are generally overloaded, rather than simply respond slowly.
-Finally, many services will have quotas on calls, perhaps a number of operations per hour or day, usually related to a service plan or price.
-When these quotas are exceeded services must also provide immediate, actionable errors.
-Quotas and Limits should be scoped to a customer unit: a subscription, a tenant, an application, a plan, or without any other identification a range of ip addresses…as appropriate to the service goals so that the load is properly shared and one unit is not interfering with another.
-
-### 14.2. Return Codes (429 vs 503)
-HTTP specifies two return codes for these scenarios: '429 Too Many Requests' and '503 Service Unavailable'.
-Services should use 429 for cases where clients are making too many calls and can fix the situation by changing their call pattern.
-Services should respond with 503 in cases where general load or other problems outside the control of the individual callers is responsible for the service becoming slow.
-In all cases, services should also provide information suggesting how long the callers should wait before trying in again.
-Clients should respect these headers and also implement other transient fault handling techniques.
-However, there may be clients that simply retry immediately upon failure, potentially increasing the load on the service.
-To handle this, services should design so that returning 429 or 503 is as inexpensive as possible, either by putting in special fastpath code, or ideally by depending on a common frontdoor or load balancer that provides this functionality.
-
-### 14.3. Retry-After and RateLimit Headers
-The Retry-After header is the standard way for responding to clients who are being throttled.
-It is also common, but optional, in the case of limits and quotas (but not overall system load) to respond with header describing the limit that was exceeded.
-However, services across Microsoft and the industry use a wide range of different headers for this purpose.
-We recommend using three headers to describe the limit, the number of calls remaining under the limit, and the time when the limit will reset.
-However, other headers may be appropriate for specific types of limits. In all cases these must be documented.
-
-### 14.4. Service Guidance
-Services should choose time windows as appropriate for the SLAs or business objectives.
-In the case of Quotas, the Retry-After time and time window may be very long (hours, days, weeks, even months. Services use 429 to indicate the specific caller has made too many calls, and 503 to indicate that the service is load shedding but that it is not the caller’s responsibility.
-
-#### 14.4.1. Responsiveness
-1. Services MUST respond quickly in all circumstances, even when under load.
-2. Calls that take longer than 1s to respond in the 99th percentile SHOULD use the Long-Running Operation pattern
-3. Calls that take longer than 0.5s to respond in the 99th percentile should strongly consider the LRO pattern
-4. Services SHOULD NOT introduce sleeps, pauses, etc. that block callers or are not actionable (“tar-pitting”).
-
-#### 14.4.2. Rate Limits and Quotas
-When a caller has made too many calls
-
-1. Services MUST return a 429 code
-2. Services MUST return a standard error response describing the specifics so that a programmer can make appropriate changes
-3. Services MUST return a Retry-After header that indicates how long clients should wait before retrying
-4. Services MAY return RateLimit headers that document the limit or quota that has been exceeded
-5. Services MAY return RateLimit-Limit: the number of calls the client is allowed to make in a time window
-6. Services MAY return RateLimit-Remaining: the number of calls remaining in the time window
-7. Services MAY return RateLimit-Reset: the time at which the window resets in UTC epoch seconds
-8. Services MAY return other service specific RateLimit headers as appropriate for more detailed information or specific limits or quotas
-
-#### 14.4.3. Overloaded services
-When services are generally overloaded and load shedding
-
-1. Services MUST Return a 503 code
-2. Services MUST Return a standard error response (see 7.10.2) describing the specifics so that a programmer can make appropriate changes
-3. Services MUST Return a Retry-After header that indicates how long clients should wait before retrying
-4. In the 503 case, the service SHOULD NOT return RateLimit headers
-
-#### 14.4.4. Example Response
-
-```http
-HTTP/1.1 429 Too Many Requests
-Content-Type: application/json
-Retry-After: 5
-RateLimit-Limit: 1000
-RateLimit-Remaining: 0
-RateLimit-Reset: 1538152773
-{
- "error": {
- "code": "requestLimitExceeded",
- "message": "The caller has made too many requests in the time period.",
- "details": {
- "code": "RateLimit",
- "limit": "1000",
- "remaining": "0",
- "reset": "1538152773",
- }
- }
-}
-```
-
-### 14.5. Caller Guidance
-Callers include all users of the API: tools, portals, other services, not just user clients
-
-1. Callers MUST wait for a minimum of time indicated in a response with a Retry-After before retrying a request.
-2. Callers MAY assume that request is retriable after receiving a response with a Retry-After header without making any changes to the request.
-3. Clients SHOULD use shared SDKs and common transient fault libraries to implement the proper behavior
-
-See: https://docs.microsoft.com/en-us/azure/architecture/best-practices/transient-faults
-
-### 14.6. Handling callers that ignore Retry-After headers
-Ideally, 429 and 503 returns are so low cost that even clients that retry immediately can be handled.
-In these cases, if possible the service team should make an effort to contact or fix the client.
-If it is a known partner, a bug or incident should be filed.
-In extreme cases it may be necessary to use DoS style protections such as blocking the caller.
-
-## 15. Push notifications via webhooks
-### 15.1. Scope
-Services MAY implement push notifications via web hooks.
-This section addresses the following key scenario:
-
-> Push notification via HTTP Callbacks, often called Web Hooks, to publicly-addressable servers.
-
-The approach set forth is chosen due to its simplicity, broad applicability, and low barrier to entry for service subscribers.
-It's intended as a minimal set of requirements and as a starting point for additional functionality.
-
-### 15.2. Principles
-The core principles for services that support web hooks are:
-
-1. Services MUST implement at least a poke/pull model. In the poke/pull model, a notification is sent to a client, and clients then send a request to get the current state or the record of change since their last notification. This approach avoids complexities around message ordering, missed messages, and change sets. Services MAY add more data to provide rich notifications.
-2. Services MUST implement the challenge/response protocol for configuring callback URLs.
-3. Services SHOULD have a recommended age-out period, with flexibility for services to vary based on scenario.
-4. Services SHOULD allow subscriptions that are raising successful notifications to live forever and SHOULD be tolerant of reasonable outage periods.
-5. Firehose subscriptions MUST be delivered only over HTTPS. Services SHOULD require other subscription types to be HTTPS. See the "Security" section for more details.
-
-### 15.3. Types of subscriptions
-There are two subscription types, and services MAY implement either, both, or none.
-The supported subscription types are:
-
-1. Firehose subscriptions – a subscription is manually created for the subscribing application, typically in an app registration portal. Notifications of activity that any users have consented to the app receiving are sent to this single subscription.
-2. Per-resource subscriptions – the subscribing application uses code to programmatically create a subscription at runtime for some user-specific entity(s).
-
-Services that support both subscription types SHOULD provide differentiated developer experiences for the two types:
-
-1. Firehose – Services MUST NOT require developers to create code except to directly verify and respond to notifications. Services MUST provide administrative UI for subscription management. Services SHOULD NOT assume that end users are aware of the subscription, only the subscribing application's functionality.
-2. Per-user – Services MUST provide an API for developers to create and manage subscriptions as part of their app as well as verifying and responding to notifications. Services MAY expect end users to be aware of subscriptions and MUST allow end users to revoke subscriptions where they were created directly in response to user actions.
-
-### 15.4. Call sequences
-The call sequence for a firehose subscription MUST follow the diagram below.
-It shows manual registration of application and subscription, and then the end user making use of one of the service's APIs.
-At this part of the flow, two things MUST be stored:
-
-1. The service MUST store the end user's act of consent to receiving notifications from this specific application (typically a background usage OAUTH scope.)
-2. The subscribing application MUST store the end user's tokens in order to call back for details once notified of changes.
-
-The final part of the sequence is the notification flow itself.
-
-Non-normative implementation guidance: A resource in the service changes and the service needs to run the following logic:
-
-1. Determine the set of users who have access to the resource, and could thus expect apps to receive notifications about it on their behalf.
-2. See which of those users have consented to receiving notifications and from which apps.
-3. See which apps have registered a firehose subscription.
-4. Join 1, 2, 3 to produce the concrete set of notifications that must be sent to apps.
-
-It should be noted that the act of user consent and the act of setting up a firehose subscription could arrive in either order.
-Services SHOULD send notifications with setup processed in either order.
-
-![Firehose subscription setup][websequencediagram-firehose-subscription-setup]
-
-For a per-user subscription, app registration is either manual or automated.
-The call flow for a per-user subscription MUST follow the diagram below.
-It shows the end user making use of one of the service's APIs, and again, the same two things MUST be stored:
-
-1. The service MUST store the end user's act of consent to receiving notifications from this specific application (typically a background usage OAUTH scope).
-2. The subscribing application MUST store the end user's tokens in order to call back for details once notified of changes.
-
-In this case, the subscription is set up programmatically using the end-user's token from the subscribing application.
-The app MUST store the ID of the registered subscription alongside the user tokens.
-
-Non normative implementation guidance: In the final part of the sequence, when an item of data in the service changes and the service needs to run the following logic:
-
-1. Find the set of subscriptions that correspond via resource to the data that changed.
-2. For subscriptions created under an app+user token, send a notification to the app per subscription with the subscription ID and user id of the subscription-creator.
-- For subscriptions created with an app only token, check that the owner of the changed data or any user that has visibility of the changed data has consented to notifications to the application, and if so send a set of notifications per user id to the app per subscription with the subscription ID.
-
- ![User subscription setup][websequencediagram-user-subscription-setup]
-
-### 15.5. Verifying subscriptions
-When subscriptions change either programmatically or in response to change via administrative UI portals, the subscribing service needs to be protected from malicious or unexpected calls from services pushing potentially large volumes of notification traffic.
-
-For all subscriptions, whether firehose or per-user, services MUST send a verification request as part of creation or modification via portal UI or API request, before sending any other notifications.
-
-Verification requests MUST be of the following format as an HTTP/HTTPS POST to the subscription's _notificationUrl_.
-
-```http
-POST https://{notificationUrl}?validationToken={randomString}
-ClientState: clientOriginatedOpaqueToken (if provided by client on subscription-creation)
-Content-Length: 0
-```
-
-For the subscription to be set up, the application MUST respond with 200 OK to this request, with the _validationToken_ value as the sole entity body.
-Note that if the _notificationUrl_ contains query parameters, the _validationToken_ parameter must be appended with an `&`.
-
-If any challenge request does not receive the prescribed response within 5 seconds of sending the request, the service MUST return an error, MUST NOT create the subscription, and MUST NOT send further requests or notifications to _notificationUrl_.
-
-Services MAY perform additional validations on URL ownership.
-
-### 15.6. Receiving notifications
-Services SHOULD send notifications in response to service data changes that do not include details of the changes themselves, but include enough information for the subscribing application to respond appropriately to the following process:
-
-1. Applications MUST identify the correct cached OAuth token to use for a callback
-2. Applications MAY look up any previous delta token for the relevant scope of change
-3. Applications MUST determine the URL to call to perform the relevant query for the new state of the service, which MAY be a delta query.
-
-Services that are providing notifications that will be relayed to end users MAY choose to add more detail to notification packets in order to reduce incoming call load on their service.
- Such services MUST be clear that notifications are not guaranteed to be delivered and may be lossy or out of order.
-
-Notifications MAY be aggregated and sent in batches.
-Applications MUST be prepared to receive multiple events inside a single push notification.
-
-The service MUST send all Web Hook data notifications as POST requests.
-
-Services MUST allow for a 30-second timeout for notifications.
-If a timeout occurs or the application responds with a 5xx response, then the service SHOULD retry the notification with exponential back-off.
-All other responses will be ignored.
-
-The service MUST NOT follow 301/302 redirect requests.
-
-#### 15.6.1. Notification payload
-The basic format for notification payloads is a list of events, each containing the id of the subscription whose referenced resources have changed, the type of change, the resource that should be consumed to identify the exact details of the change and sufficient identity information to look up the token required to call that resource.
-
-For a firehose subscription, a concrete example of this may look like:
-
-```json
-{
- "value": [
- {
- "subscriptionId": "32b8cbd6174ab18b",
- "resource": "https://api.contoso.com/v1.0/users/user@contoso.com/files?$delta",
- "userId" : "",
- "tenantId" : ""
- }
- ]
-}
-```
-
-For a per-user subscription, a concrete example of this may look like:
-
-```json
-{
- "value": [
- {
- "subscriptionId": "32b8cbd6174ab183",
- "clientState": "clientOriginatedOpaqueToken",
- "expirationDateTime": "2016-02-04T11:23Z",
- "resource": "https://api.contoso.com/v1.0/users/user@contoso.com/files/$delta",
- "userId" : "",
- "tenantId" : ""
- },
- {
- "subscriptionId": "97b391179fa22",
- "clientState ": "clientOriginatedOpaqueToken",
- "expirationDateTime": "2016-02-04T11:23Z",
- "resource": "https://api.contoso.com/v1.0/users/user@contoso.com/files/$delta",
- "userId" : "",
- "tenantId" : ""
- }
- ]
-}
-```
-
-Following is a detailed description of the JSON payload.
-
-A notification item consists a top-level object that contains an array of events, each of which identified the subscription due to which this notification is being sent.
-
-Field | Description
------ | --------------------------------------------------------------------------------------------------
-value | Array of events that have been raised within the subscription’s scope since the last notification.
-
-Each item of the events array contains the following properties:
-
-Field | Description
------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-subscriptionId | The id of the subscription due to which this notification has been sent. Services MUST provide the *subscriptionId* field.
-clientState | Services MUST provide the *clientState* field if it was provided at subscription creation time.
-expirationDateTime | Services MUST provide the *expirationDateTime* field if the subscription has one.
-resource | Services MUST provide the resource field. This URL MUST be considered opaque by the subscribing application. In the case of a richer notification it MAY be subsumed by message content that implicitly contains the resource URL to avoid duplication. If a service is providing this data as part of a more detailed data packet, then it need not be duplicated.
-userId | Services MUST provide this field for user-scoped resources. In the case of user-scoped resources, the unique identifier for the user should be used. In the case of resources shared between a specific set of users, multiple notifications must be sent, passing the unique identifier of each user. For tenant-scoped resources, the user id of the subscription should be used.
-tenantId | Services that wish to support cross-tenant requests SHOULD provide this field. Services that provide notifications on tenant-scoped data MUST send this field.
-
-### 15.7. Managing subscriptions programmatically
-For per-user subscriptions, an API MUST be provided to create and manage subscriptions.
-The API must support at least the operations described here.
-
-#### 15.7.1. Creating subscriptions
-A client creates a subscription by issuing a POST request against the subscriptions resource.
-The subscription namespace is client-defined via the POST operation.
-
-```
-https://api.contoso.com/apiVersion/$subscriptions
-```
-
-The POST request contains a single subscription object to be created.
-That subscription object has the following properties:
-
-Property Name | Required | Notes
---------------- | -------- | ---------------------------------------------------------------------------------------------------------------------------
-resource | Yes | Resource path to watch.
-notificationUrl | Yes | The target web hook URL.
-clientState | No | Opaque string passed back to the client on all notifications. Callers may choose to use this to provide tagging mechanisms.
-
-If the subscription was successfully created, the service MUST respond with the status code 201 CREATED and a body containing at least the following properties:
-
-Property Name | Required | Notes
------------------- | -------- | -------------------------------------------------------------------------------------------
-id | Yes | Unique ID of the new subscription that can be used later to update/delete the subscription.
-expirationDateTime | No | Uses existing Microsoft REST API Guidelines defined time formats.
-
-Creation of subscriptions SHOULD be idempotent.
-The combination of properties scoped to the auth token, provides a uniqueness constraint.
-
-Below is an example request using a User + Application principal to subscribe to notifications from a file:
-
-```http
-POST https://api.contoso.com/files/v1.0/$subscriptions HTTP 1.1
-Authorization: Bearer {UserPrincipalBearerToken}
-
-{
- "resource": "http://api.service.com/v1.0/files/file1.txt",
- "notificationUrl": "https://contoso.com/myCallbacks",
- "clientState": "clientOriginatedOpaqueToken"
-}
-```
-
-The service SHOULD respond to such a message with a response format minimally like this:
-
-```json
-{
- "id": "32b8cbd6174ab18b",
- "expirationDateTime": "2016-02-04T11:23Z"
-}
-```
-
-Below is an example using an Application-Only principal where the application is watching all files to which it's authorized:
-
-```http
-POST https://api.contoso.com/files/v1.0/$subscriptions HTTP 1.1
-Authorization: Bearer {ApplicationPrincipalBearerToken}
-
-{
- "resource": "All.Files",
- "notificationUrl": "https://contoso.com/myCallbacks",
- "clientState": "clientOriginatedOpaqueToken"
-}
-```
-
-The service SHOULD respond to such a message with a response format minimally like this:
-
-```json
-{
- "id": "8cbd6174abb391179",
- "expirationDateTime": "2016-02-04T11:23Z"
-}
-```
-
-#### 15.7.2. Updating subscriptions
-Services MAY support amending subscriptions.
- To update the properties of an existing subscription, clients use PATCH requests providing the ID and the properties that need to change.
-Omitted properties will retain their values.
-To delete a property, assign a value of JSON null to it.
-
-As with creation, subscriptions are individually managed.
-
-The following request changes the notification URL of an existing subscription:
-
-```http
-PATCH https://api.contoso.com/files/v1.0/$subscriptions/{id} HTTP 1.1
-Authorization: Bearer {UserPrincipalBearerToken}
-
-{
- "notificationUrl": "https://contoso.com/myNewCallback"
-}
-```
-
-If the PATCH request contains a new _notificationUrl_, the server MUST perform validation on it as described above.
-If the new URL fails to validate, the service MUST fail the PATCH request and leave the subscription in its previous state.
-
-The service MUST return an empty body and `204 No Content` to indicate a successful patch.
-
-The service MUST return an error body and status code if the patch failed.
-
-The operation MUST succeed or fail atomically.
-
-#### 15.7.3. Deleting subscriptions
-Services MUST support deleting subscriptions.
-Existing subscriptions can be deleted by making a DELETE request against the subscription resource:
-
-```http
-DELETE https://api.contoso.com/files/v1.0/$subscriptions/{id} HTTP 1.1
-Authorization: Bearer {UserPrincipalBearerToken}
-```
-
-As with update, the service MUST return `204 No Content` for a successful delete, or an error body and status code to indicate failure.
-
-#### 15.7.4. Enumerating subscriptions
-To get a list of active subscriptions, clients issue a GET request against the subscriptions resource using a User + Application or Application-Only bearer token:
-
-```http
-GET https://api.contoso.com/files/v1.0/$subscriptions HTTP 1.1
-Authorization: Bearer {UserPrincipalBearerToken}
-```
-
-The service MUST return a format as below using a User + Application principal bearer token:
-
-```json
-{
- "value": [
- {
- "id": "32b8cbd6174ab18b",
- "resource": " http://api.contoso.com/v1.0/files/file1.txt",
- "notificationUrl": "https://contoso.com/myCallbacks",
- "clientState": "clientOriginatedOpaqueToken",
- "expirationDateTime": "2016-02-04T11:23Z"
- }
- ]
-}
-```
-
-An example that may be returned using Application-Only principal bearer token:
-
-```json
-{
- "value": [
- {
- "id": "6174ab18bfa22",
- "resource": "All.Files ",
- "notificationUrl": "https://contoso.com/myCallbacks",
- "clientState": "clientOriginatedOpaqueToken",
- "expirationDateTime": "2016-02-04T11:23Z"
- }
- ]
-}
-```
-
-### 15.8. Security
-All service URLs must be HTTPS (that is, all inbound calls MUST be HTTPS). Services that deal with Web Hooks MUST accept HTTPS.
-
-We recommend that services that allow client defined Web Hook Callback URLs SHOULD NOT transmit data over HTTP.
-This is because information can be inadvertently exposed via client, network, server logs and other mechanisms.
-
-However, there are scenarios where the above recommendations cannot be followed due to client endpoint or software limitations.
-Consequently, services MAY allow web hook URLs that are HTTP.
-
-Furthermore, services that allow client defined HTTP web hooks callback URLs SHOULD be compliant with privacy policy specified by engineering leadership.
-This will typically include recommending that clients prefer SSL connections and adhere to special precautions to ensure that logs and other service data collection are properly handled.
-
-For example, services may not want to require developers to generate certificates to onboard.
-Services might only enable this on test accounts.
-
-## 16. Unsupported requests
-RESTful API clients MAY request functionality that is currently unsupported.
-RESTful APIs MUST respond to valid but unsupported requests consistent with this section.
-
-### 16.1. Essential guidance
-RESTful APIs will often choose to limit functionality that can be performed by clients.
-For instance, auditing systems allow records to be created but not modified or deleted.
-Similarly, some APIs will expose collections but require or otherwise limit filtering and ordering criteria, or MAY not support client-driven pagination.
-
-### 16.2. Feature allow list
-If a service does not support any of the below API features, then an error response MUST be provided if the feature is requested by a caller.
-The features are:
-- Key Addressing in a collection, such as: `https://api.contoso.com/v1.0/people/user1@contoso.com`
-- Filtering a collection by a property value, such as: `https://api.contoso.com/v1.0/people?$filter=name eq 'david'`
-- Filtering a collection by range, such as: `http://api.contoso.com/v1.0/people?$filter=hireDate ge 2014-01-01 and hireDate le 2014-12-31`
-- Client-driven pagination via $top and $skip, such as: `http://api.contoso.com/v1.0/people?$top=5&$skip=2`
-- Sorting by $orderBy, such as: `https://api.contoso.com/v1.0/people?$orderBy=name desc`
-- Providing $delta tokens, such as: `https://api.contoso.com/v1.0/people?$delta`
-
-#### 16.2.1. Error response
-Services MUST provide an error response if a caller requests an unsupported feature found in the feature allow list.
-The error response MUST be an HTTP status code from the 4xx series, indicating that the request cannot be fulfilled.
-Unless a more specific error status is appropriate for the given request, services SHOULD return "400 Bad Request" and an error payload conforming to the error response guidance provided in the Microsoft REST API Guidelines.
-Services SHOULD include enough detail in the response message for a developer to determine exactly what portion of the request is not supported.
-
-Example:
-
-```http
-GET https://api.contoso.com/v1.0/people?$orderBy=name HTTP/1.1
-Accept: application/json
-```
-
-```http
-HTTP/1.1 400 Bad Request
-Content-Type: application/json
-
-{
- "error": {
- "code": "ErrorUnsupportedOrderBy",
- "message": "Ordering by name is not supported."
- }
-}
-```
-
-## 17. Naming guidelines
-### 17.1. Approach
-Naming policies should aid developers in discovering functionality without having to constantly refer to documentation.
-Use of common patterns and standard conventions greatly aids developers in correctly guessing common property names and meanings.
-Services SHOULD use verbose naming patterns and SHOULD NOT use abbreviations other than acronyms that are the dominant mode of expression in the domain being represented by the API, (e.g. Url).
-
-### 17.2. Casing
-- Acronyms SHOULD follow the casing conventions as though they were regular words (e.g. Url).
-- All identifiers including namespaces, entityTypes, entitySets, properties, actions, functions and enumeration values SHOULD use lowerCamelCase.
-- HTTP headers are the exception and SHOULD use standard HTTP convention of Capitalized-Hyphenated-Terms.
-
-### 17.3. Names to avoid
-Certain names are so overloaded in API domains that they lose all meaning or clash with other common usages in domains that cannot be avoided when using REST APIs, such as OAUTH.
-Services SHOULD NOT use the following names:
-- Context
-- Scope
-- Resource
-
-### 17.4. Forming compound names
-- Services SHOULD avoid using articles such as 'a', 'the', 'of' unless needed to convey meaning.
- - e.g. names such as aUser, theAccount, countOfBooks SHOULD NOT be used, rather user, account, bookCount SHOULD be preferred.
-- Services SHOULD add a type to a property name when not doing so would cause ambiguity about how the data is represented or would cause the service not to use a common property name.
-- When adding a type to a property name, services MUST add the type at the end, e.g. createdDateTime.
-
-### 17.5. Identity properties
-- Services MUST use string types for identity properties.
-- For OData services, the service MUST use the OData @id property to represent the canonical identifier of the resource.
-- Services MAY use the simple 'id' property to represent a local or legacy primary key value for a resource.
-- Services SHOULD use the name of the relationship postfixed with 'Id' to represent a foreign key to another resource, e.g. subscriptionId.
- - The content of this property SHOULD be the canonical ID of the referenced resource.
-
-### 17.6. Date and time properties
-
-- For properties requiring both date and time, services MUST use the suffix 'DateTime'.
-- For properties requiring only date information without specifying time, services MUST use the suffix 'Date', e.g. birthDate.
-- For properties requiring only time information without specifying date, services MUST use the suffix 'Time', e.g. appointmentStartTime.
-
-### 17.7. Name properties
-- For the overall name of a resource typically shown to users, services MUST use the property name 'displayName'.
-- Services MAY use other common naming properties, e.g. givenName, surname, signInName.
-
-### 17.8. Collections and counts
-- Services MUST name collections as plural nouns or plural noun phrases using correct English.
-- Services MAY use simplified English for nouns that have plurals not in common verbal usage.
- - e.g. schemas MAY be used instead of schemata.
-- Services MUST name counts of resources with a noun or noun phrase suffixed with 'Count'.
-
-### 17.9. Common property names
-Where services have a property, whose data matches the names below, the service MUST use the name from this table.
-This table will grow as services add terms that will be more commonly used.
-Service owners adding such terms SHOULD propose additions to this document.
-
-| |
-|------------- |
- attendees |
- body |
- createdDateTime |
- childCount |
- children |
- contentUrl |
- country |
- createdBy |
- displayName |
- errorUrl |
- eTag |
- event |
- expirationDateTime |
- givenName |
- jobTitle |
- kind |
- id |
- lastModifiedDateTime |
- location |
- memberOf |
- message |
- name |
- owner |
- people |
- person |
- postalCode |
- photo |
- preferredLanguage |
- properties |
- signInName |
- surname |
- tags |
- userPrincipalName |
- webUrl |
-
-## 18. Appendix
-### 18.1. Sequence diagram notes
-All sequence diagrams in this document are generated using the [WebSequenceDiagrams.com](https://www.websequencediagrams.com/). To generate them, paste the text below into the web tool.
-
-#### 18.1.1. Push notifications, per user flow
-
-```
-=== Begin Text ===
-note over Developer, Automation, App Server:
- An App Developer like MovieMaker
- Wants to integrate with primary service like Dropbox
-end note
-note over DB Portal, DB App Registration, DB Notifications, DB Auth, DB Service: The primary service like Dropbox
-note over Client: The end users' browser or installed app
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Manual App Registration
-
-
-Developer <--> DB Portal : Login into Portal, App Registration UX
-DB Portal -> +DB App Registration: App Name etc.
-note over DB App Registration: Confirm Portal Access Token
-
-DB App Registration -> -DB Portal: App ID
-DB Portal <--> App Server: Developer copies App ID
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Manual Notification Registration
-
-Developer <--> DB Portal: webhook registration UX
-DB Portal -> +DB Notifications: Register: App Server webhook URL, Scope, App ID
-Note over DB Notifications : Confirm Portal Access Token
-DB Notifications -> -DB Portal: notification ID
-DB Portal --> App Server : Developer may copy notification ID
-
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Client Authorization
-
-Client -> +App Server : Request access to DB protected information
-App Server -> -Client : Redirect to DB Authorization endpoint with authorization request
-Client -> +DB Auth : Redirected authorization request
-Client <--> DB Auth : Authorization UX
-DB Auth -> -Client : Redirect back to App Server with code
-Client -> +App Server : Redirect request back to access server with access code
-App Server -> +DB Auth : Request tokens with access code
-note right of DB Service: Cache that this User ID provided access to App ID
-DB Auth -> -App Server : Response with access, refresh, and ID tokens
-note right of App Server : Cache tokens by user ID
-App Server -> -Client : Return information to client
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Notification Flow
-
-Client <--> DB Service: Changes to user data - typical via interacting with App Server via Client
-DB Service -> App Server : Notification with notification ID and user ID
-App Server -> +DB Service : Request changed information with cached access tokens and "since" token
-note over DB Service: Confirm User Access Token
-DB Service -> -App Server : Response with data and new "since" token
-note right of App Server: Update status and cache new "since" token
-=== End Text ===
-```
-
-#### 18.1.2. Push notifications, firehose flow
-
-```
-=== Begin Text ===
-note over Developer, Automation, App Server:
- An App Developer like MovieMaker
- Wants to integrate with primary service like Dropbox
-end note
-note over DB Portal, DB App Registration, DB Notifications, DB Auth, DB Service: The primary service like Dropbox
-note over Client: The end users' browser or installed app
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : App Registration
-
-alt Automated app registration
- Developer <--> Automation: Configure
- Automation -> +DB App Registration: App Name etc.
- note over DB App Registration: Confirm App Access Token
- DB App Registration -> -Automation: App ID, App Secret
- Automation --> App Server : Embed App ID, App Secret
-else Manual app registration
- Developer <--> DB Portal : Login into Portal, App Registration UX
- DB Portal -> +DB App Registration: App Name etc.
- note over DB App Registration: Confirm Portal Access Token
-
- DB App Registration -> -DB Portal: App ID
- DB Portal <--> App Server: Developer copies App ID
-end
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Client Authorization
-
-Client -> +App Server : Request access to DB protected information
-App Server -> -Client : Redirect to DB Authorization endpoint with authorization request
-Client -> +DB Auth : Redirected authorization request
-Client <--> DB Auth : Authorization UX
-DB Auth -> -Client : Redirect back to App Server with code
-Client -> +App Server : Redirect request back to access server with access code
-App Server -> +DB Auth : Request tokens with access code
-note right of DB Service: Cache that this User ID provided access to App ID
-DB Auth -> -App Server : Response with access, refresh, and ID tokens
-note right of App Server : Cache tokens by user ID
-App Server -> -Client : Return information to client
-
-
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Notification Registration
-
-App Server->+DB Notifications: Register: App server webhook URL, Scope, App ID
-note over DB Notifications : Confirm User Access Token
-DB Notifications -> -App Server: notification ID
-note right of App Server : Cache the Notification ID and User Access Token
-
-
-
-note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Notification Flow
-
-Client <--> DB Service: Changes to user data - typical via interacting with App Server via Client
-DB Service -> App Server : Notification with notification ID and user ID
-App Server -> +DB Service : Request changed information with cached access tokens and "since" token
-note over DB Service: Confirm User Access Token
-DB Service -> -App Server : Response with data and new "since" token
-note right of App Server: Update status and cache new "since" token
-
-
-
-=== End Text ===
-```
-[fielding]: https://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm
-[IANA-headers]: https://www.iana.org/assignments/message-headers/message-headers.xhtml
-[rfc-2119]: https://tools.ietf.org/html/rfc2119
-[rfc7231-7-1-1-1]: https://tools.ietf.org/html/rfc7231#section-7.1.1.1
-[rfc-7230-3-1-1]: https://tools.ietf.org/html/rfc7230#section-3.1.1
-[rfc-7231]: https://tools.ietf.org/html/rfc7231
-[rest-in-practice]: https://www.amazon.com/REST-Practice-Hypermedia-Systems-Architecture/dp/0596805829/
-[rest-on-wikipedia]: https://en.wikipedia.org/wiki/Representational_state_transfer
-[rfc-5789]: https://tools.ietf.org/html/rfc5789
-[rfc-5988]: https://tools.ietf.org/html/rfc5988
-[rfc-3339]: https://tools.ietf.org/html/rfc3339
-[rfc-5322-3-3]: https://tools.ietf.org/html/rfc5322#section-3.3
-[cors-preflight]: https://www.w3.org/TR/cors/#resource-preflight-requests
-[rfc-3864]: https://tools.ietf.org/html/rfc3864
-[odata-json-annotations]: https://docs.oasis-open.org/odata/odata-json-format/v4.0/os/odata-json-format-v4.0-os.html#_Instance_Annotations
-[cors]: https://www.w3.org/TR/access-control/
-[cors-user-credentials]: https://www.w3.org/TR/access-control/#user-credentials
-[cors-simple-headers]: https://www.w3.org/TR/access-control/#simple-header
-[rfc-4627]: https://tools.ietf.org/html/rfc4627
-[iso-8601]: https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15
-[clr-time]: https://msdn.microsoft.com/en-us/library/System.DateTime(v=vs.110).aspx
-[ecmascript-time]: https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.1
-[ole-date]: https://docs.microsoft.com/en-us/windows/desktop/api/oleauto/nf-oleauto-varianttimetosystemtime
-[ticks-time]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms724290(v=vs.85).aspx
-[unix-time]: https://msdn.microsoft.com/en-us/library/1f4c8f33.aspx
-[windows-time]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms724290(v=vs.85).aspx
-[excel-time]: https://support.microsoft.com/kb/214326?wa=wsignin1.0
-[wikipedia-iso8601-durations]: https://en.wikipedia.org/wiki/ISO_8601#Durations
-[wikipedia-iso8601-intervals]: https://en.wikipedia.org/wiki/ISO_8601#Time_intervals
-[wikipedia-iso8601-repeatingintervals]: https://en.wikipedia.org/wiki/ISO_8601#Repeating_intervals
-[principle-of-least-astonishment]: https://en.wikipedia.org/wiki/Principle_of_least_astonishment
-[odata-breaking-changes]: https://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398209
-[websequencediagram-firehose-subscription-setup]: https://www.websequencediagrams.com/cgi-bin/cdraw?lz=bm90ZSBvdmVyIERldmVsb3BlciwgQXV0b21hdGlvbiwgQXBwIFNlcnZlcjogCiAgICAgQW4AEAUAJwkgbGlrZSBNb3ZpZU1ha2VyACAGV2FudHMgdG8gaW50ZWdyYXRlIHdpdGggcHJpbWFyeSBzZXJ2aWNlADcGRHJvcGJveAplbmQgbm90ZQoAgQwLQiBQb3J0YWwsIERCAIEJBVJlZ2lzdHIAgRkHREIgTm90aWZpYwCBLAVzACEGdXRoACsFUwBgBjogVGhlAF0eAIF_CkNsaWVudAAtBmVuZCB1c2VycycgYnJvd3NlciBvciBpbnN0YWxsZWQgYXBwCgCBIQwAgiQgAIFABQCBIS8AgQoGIDogTWFudWFsAIFzEQoKCgCDAgo8LS0-AIIqCiA6IExvZ2luIGludG8Agj8JAII1ECBVWCAKACoKLT4gKwCCWBM6AIQGBU5hbWUgZXRjLgCDFQ4AGxJDb25maXJtAIEBCEFjY2VzcyBUb2tlbgoKAIM3EyAtPiAtAINkCQBnBklEAIEMCwCBVQUAhQIMAIR3CmNvcGllcwArCACCIHAAhHMMAIMKDwCDABg6IHdlYmhvb2sgcgCCeg4AgnUSAIVQDToAhXYHZXIAgwgGAIcTBgBECVVSTCwgU2NvcGUAhzIGSUQKTgCGPQwAhhwNIACDBh4AHhEAgxEPbgCBagwAgxwNAIMaDiAAgx0MbWF5IGNvcHkALREAhVtqAIZHB0F1dGhvcml6AIY7BwCGXQctPiArAIEuDVJlcXVlc3QgYQCFOQZ0byBEQiBwcm90ZWN0ZWQgaW5mb3IAiiQGCgCDBQstPiAtAIctCVJlZGlyZWN0ADYHAGwNIGVuZHBvaW50AIoWBmEADw1yAHYGAIEQDACJVAcASwtlZAAYHgCICAgAMAcAcA4AhGoGAE0FAIEdFmJhY2sgdG8AhF8NaXRoIGNvZGUAghoaaQCBagcAgToHAD0JAII-B3MAPgsAglEHAEsFAIIzDgCBXw0Agn8GdG9rZW5zACcSAI0_BXJpZ2h0IG9mAItpDUNhY2hlIHRoYXQgdGhpcyBVc2VyIElEIHByb3ZpZGVkAINNCwCIZgoAggcJAIN7D3Nwb25zAI0_BwCECgYsIHJlZnJlc2gsIGFuZCBJRACBHAcAgQMPAIYADQCBDAcAgUUGYnkAjFkFIElEAIQkG3R1cm4AhF4MIHRvIGMAjR8FAIwRagCJVw1GbG93AIYqCQCMaQgAgmoKaGFuZ2UAj3YFAIFXBWRhdGEgLSB0eXBpY2FsIHZpYQCQDgVyYWN0aW5nAJAPBgCJQQt2aWEAjnsHCgCPNgogAIhDEACKZw0AkFMFAIkBDwCDDAUAgkYWKwBNCwCHWApjAIEyBQCHRg0AhWUHYWNoAIQeDACEfwVhbmQgInNpbmNlIgCFEQYAkSQOAIR3CgCNfwcAhHQFAIpQEACBUgsAhFAcAII8BWFuZCBuZXcAYRQAhFUTOiBVcGRhdGUgc3RhdHUAgSkGAIFDBQAxEwoKCg&s=mscgen
-[websequencediagram-user-subscription-setup]: https://www.websequencediagrams.com/cgi-bin/cdraw?lz=bm90ZSBvdmVyIERldmVsb3BlciwgQXV0b21hdGlvbiwgQXBwIFNlcnZlcjogCiAgICAgQW4AEAUAJwkgbGlrZSBNb3ZpZU1ha2VyACAGV2FudHMgdG8gaW50ZWdyYXRlIHdpdGggcHJpbWFyeSBzZXJ2aWNlADcGRHJvcGJveAplbmQgbm90ZQoAgQwLQiBQb3J0YWwsIERCAIEJBVJlZ2lzdHIAgRkHREIgTm90aWZpYwCBLAVzACEGdXRoACsFUwBgBjogVGhlAF0eAIF_CkNsaWVudAAtBmVuZCB1c2VycycgYnJvd3NlciBvciBpbnN0YWxsZWQgYXBwCgCBIQwAgiQgAIFABQCBIS8AgQoGIDoAgWwRCgphbHQAgyUIAIEHBiByABQMICAAgxsLPC0tPgCDTws6IENvbmZpZ3VyZQogIACDaAsgLT4gKwCCWBMAegZOYW1lIGV0Yy4AhAgFAIMaDQAfEgBdBXJtAIQ_BUFjY2VzcyBUb2tlAIETBgCDOxIgLT4gLQCBFgxBcHAgSUQAhHwIY3JldACBGxAtPgCFFgsgOiBFbWJlZAAkFGVsc2UgTWFudWFsAIIEJACEbQkgOiBMb2dpbiBpbnRvAIUBCQCBKRFVWACGGAUALQoAgh8mAIIZKwCBCAcAgjoNAIIsHACGLwkAgj8IAIESDgCECAYAh1ELAIdFCmNvcGllcwAuCGVuZACEeGoAhWQHQXV0aG9yaXoAhV8HAIV6By0-ICsAg2ANUmVxdWVzdCBhAIRVBnRvIERCIHByb3RlY3RlZCBpbmZvcgCJQQYKAIQaCy0-IC0AhkoJUmVkaXJlY3QANgcAbA0gZW5kcG9pbnQAiTMGYQAPDXIAdgYAgRAMAIhxBwBLC2VkABgeAIRjCAAwB0EAcQxVWAoASQgAgRwWYmFjayB0bwCFdAwAilwFY29kZQCCGRppAIFpBwCBOQcAPQkAgj0HcwA-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&s=mscgen
diff --git a/README.md b/README.md
index 8c88ec68..731da41c 100644
--- a/README.md
+++ b/README.md
@@ -1,29 +1,19 @@
- # NOTICE TO READERS
-
- ## Guidance for Azure service teams
-Azure service teams should use companion documents, [Azure REST API Guidelines](./azure/Guidelines.md) and [Considerations for Service Design](./azure/ConsiderationsForServiceDesign.md), when building or modifying their services. These documents provide a refined set of guidance targeted specifically for Azure services. For more information please refer to the [README](./azure/README.md) in the Azure folder.
-
-## Guidance for Microsoft Graph service teams
- Microsoft Graph service teams should reference the companion document, [Graph REST API Guidelines](./graph/GuidelinesGraph.md) when building or modifying their services.
+# Microsoft REST API Guidelines
+Thank you for your interest in the Microsoft REST API Guidelines. If you have landed here, you're probably interested in learning about APIs. If so, you are in the right place!
+We publish these guidelines here with the aim of fostering dialogue and learning in the API community at large. We further hope that these guidelines might encourage other organizations to create guidelines that are appropriate for them and in turn, if they're able, to publish theirs.
-In the process of building many of Microsoft's highest scale services, the Microsoft Graph team found the Microsoft API guidelines tremendously useful as a baseline. However, there are several areas where we need to provide more clarity on how developers should describe their APIs. The companion document, [Graph REST API Guidelines](./graph/GuidelinesGraph.md) is a set of amendments and clarifications for Microsoft Graph that act as further reading. Recognizing that two documents is a lot for a new API designer to absorb, our plan is to follow the approach Azure have taken and roll out guidelines for Microsoft Graph into a single consolidated document.
+### Guidance for Azure service teams
+Azure service teams should reference the companion documents, [Azure REST API Guidelines](./azure/Guidelines.md) and [Considerations for Service Design](./azure/ConsiderationsForServiceDesign.md), when building or modifying their services. These documents provide a refined set of guidance targeted specifically for Azure services. For more information, please refer to the [README](./azure/README.md) in the Azure folder.
----
-
-## Microsoft REST API Guidelines
-The [Microsoft REST API Guidelines](Guidelines.md) are Microsoft's internal company-wide REST API design guidelines.
-Teams at Microsoft typically reference this document when setting API design policy.
-They may additionally create documents specific to their team, adding further guidance or making adjustments as appropriate to their circumstances.
-
-We publish these guidelines here with the aim of fostering dialogue and learning in the API community at large.
-We further hope that these guidelines may encourage other organizations to create guidelines that are appropriate for them and in turn, if they are able, to publish theirs.
+### Guidance for Microsoft Graph service teams
+Graph service teams should reference the companion document, [Microsoft Graph REST API Guidelines](./graph/GuidelinesGraph.md) when building or modifying their services. This document and the associated pattern catalog provide a refined set of guidance targeted specifically for Microsoft Graph services.
[](https://creativecommons.org/licenses/by/4.0/)
## Code of Conduct
-This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
+This project adopts the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information, see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
## This repository
-This repository contains a collection of documents and related materials supporting the overall Microsoft REST API Guidelines initiative. To contribute to this repository, please see the [contribution guidelines][contribution-guidance].
+This repository contains a collection of documents and related materials supporting the overall Microsoft REST API Guidelines initiative. To contribute to this repository, see the [contribution guidelines][contribution-guidance].
[contribution-guidance]: CONTRIBUTING.md
diff --git a/azure/ConsiderationsForServiceDesign.md b/azure/ConsiderationsForServiceDesign.md
index 0b37c2f4..8dc3a480 100644
--- a/azure/ConsiderationsForServiceDesign.md
+++ b/azure/ConsiderationsForServiceDesign.md
@@ -1,13 +1,16 @@
# Considerations for Service Design
-
+
+
## History
| Date | Notes |
| ----------- | -------------------------------------------------------------- |
+| 2024-Mar-17 | Updated LRO guidelines |
+| 2024-Jan-17 | Added guidelines on returning string offsets & lengths |
| 2022-Jul-15 | Update guidance on long-running operations |
-| 2022-Feb-01 | Updated error guidance |
+| 2022-Feb-01 | Updated error guidance |
| 2021-Sep-11 | Add long-running operations guidance |
| 2021-Aug-06 | Updated Azure REST Guidelines per Azure API Stewardship Board. |
@@ -22,19 +25,18 @@ Azure Service teams should engage the Azure HTTP/REST Stewardship Board early in
It is critically important to design your service to avoid disrupting users as the API evolves:
-:white_check_mark: **DO** implement API versioning starting with the very first release of the service.
+:white_check_mark: **DO** implement API versioning starting with the very first release of the service.
-:white_check_mark: **DO** ensure that customer workloads never break
+:white_check_mark: **DO** ensure that customer workloads never break
-:white_check_mark: **DO** ensure that customers are able to adopt a new version of service or SDK client library **without requiring code changes**
+:white_check_mark: **DO** ensure that customers are able to adopt a new version of service or SDK client library **without requiring code changes**
## Azure Management Plane vs Data Plane
_Note: Developing a new service requires the development of at least 1 (management plane) API and potentially one or more additional (data plane) APIs. When reviewing v1 service APIs, we see common advice provided during the review._
A **management plane** API is implemented through the Azure Resource Manager (ARM) and is used to provision and control the operational state of resources.
A **data plane** API is used by developers to implement applications. Occasionally, some operations are useful for provisioning/control and applications. In this case, the operation can appear in both APIs.
-Although, best practices and patterns described in this document apply to all HTTP/REST APIs, they are especially important for **data plane** services because it is the primary interface for developers using your service. The **management plane** APIs may have other preferred practices based on [the conventions of the Azure ARM](https://github.com/Azure/azure-resource-manager-rpc).
-
+Although, best practices and patterns described in this document apply to all HTTP/REST APIs, they are especially important for **data plane** services because it is the primary interface for developers using your service. The **management plane** APIs may have other preferred practices based on the conventions of the [Azure RPC](https://aka.ms/azurerpc).
## Start with the Developer Experience
A great API starts with a well thought out and designed service. Your service should define simple/understandable abstractions with each given a clear name that you use consistently throughout your API and documentation. There must also be an unambiguous relationship between these abstractions.
@@ -62,27 +64,27 @@ _For this reason, it is **much better** to ship with fewer features and only add
Focusing on hero scenarios reduces development, support, and maintenance costs; enables teams to align and reach consensus faster; and accelerates the time to delivery. A telltale sign of a service that has not focused on hero scenarios is "API drift," where endpoints are inconsistent, incomplete, or juxtaposed to one another.
-:white_check_mark: **DO** define "hero scenarios" first including abstractions, naming, relationships, and then define the API describing the operations required
+:white_check_mark: **DO** define "hero scenarios" first including abstractions, naming, relationships, and then define the API describing the operations required.
-:white_check_mark: **DO** provide example code demonstrating the "Hero Scenarios"
+:white_check_mark: **DO** provide example code demonstrating the "Hero Scenarios".
-:white_check_mark: **DO** consider how your abstractions will be represented in different high-level languages.
+:white_check_mark: **DO** consider how your abstractions will be represented in different high-level languages.
-:white_check_mark: **DO** develop code examples in at least one dynamically typed language (for example, Python or JavaScript) and one statically typed language (for example, Java or C#) to illustrate your abstractions and high-level language representations.
+:white_check_mark: **DO** develop code examples in at least one dynamically typed language (for example, Python or JavaScript) and one statically typed language (for example, Java or C#) to illustrate your abstractions and high-level language representations.
-:no_entry: **DO NOT** proactively add APIs for speculative features customers might want
+:no_entry: **DO NOT** proactively add APIs for speculative features customers might want.
### Start with your API Definition
Understanding how your service is used and defining its model and interaction patterns--its API--should be one of the earliest activities a service team undertakes. It reflects the abstractions & naming decisions and makes it easy for developers to implement the hero scenarios.
-:white_check_mark: **DO** create an [OpenAPI Definition](https://github.com/OAI/OpenAPI-Specification/blob/main/versions/2.0.md) (with [autorest extensions](https://github.com/Azure/autorest/blob/master/docs/extensions/readme.md)) describing the service. The OpenAPI definition is a key element of the Azure SDK plan and is essential for documentation, usability and discoverability of services.
+:white_check_mark: **DO** create an [OpenAPI description](https://github.com/OAI/OpenAPI-Specification/blob/main/versions/2.0.md) (with [autorest extensions](https://github.com/Azure/autorest/blob/master/docs/extensions/readme.md)) for the service API. The OpenAPI description is a key element of the Azure SDK plan and is essential for documentation, usability and discoverability of service APIs.
## Design for Change Resiliency
As you build out your service and API, there are a number of decisions that can be made up front that add resiliency to client implementations. Addressing these as early as possible will help you iterate faster and avoid breaking changes.
-:ballot_box_with_check: **YOU SHOULD** use extensible enumerations. Extensible enumerations are modeled as strings - expanding an extensible enumeration is not a breaking change.
+:ballot_box_with_check: **YOU SHOULD** use extensible enumerations. Extensible enumerations are modeled as strings - expanding an extensible enumeration is not a breaking change.
-:ballot_box_with_check: **YOU SHOULD** implement [conditional requests](https://tools.ietf.org/html/rfc7232) early. This allows you to support concurrency, which tends to be a concern later on.
+:ballot_box_with_check: **YOU SHOULD** implement [conditional requests](https://tools.ietf.org/html/rfc7232) early. This allows you to support concurrency, which tends to be a concern later on.
## Use Good Names
@@ -98,43 +100,43 @@ Use common patterns and standard conventions to aid developers in correctly gues
Use verbose naming patterns and avoid abbreviations other than
well-known acronyms in your service domain.
-:heavy_check_mark: **DO** use the same name for the same concept and different names for different concepts wherever possible.
+:white_check_mark: **DO** use the same name for the same concept and different names for different concepts wherever possible.
### Recommended Naming Conventions
The following are recommended naming conventions for Azure services:
-:heavy_check_mark: **DO** name collections as plural nouns or plural noun phrases using correct English.
+:white_check_mark: **DO** name collections as plural nouns or plural noun phrases using correct English.
-:heavy_check_mark: **DO** name values that are not collections as singular nouns or singular noun phrases.
+:white_check_mark: **DO** name values that are not collections as singular nouns or singular noun phrases.
-:ballot_box_with_check: **YOU SHOULD** should place the adjective before the noun in names that contain both a noun and an adjective.
+:ballot_box_with_check: **YOU SHOULD** should place the adjective before the noun in names that contain both a noun and an adjective.
For example, `collectedItems` not `itemsCollected`
-:ballot_box_with_check: **YOU SHOULD** case all acronyms as though they were regular words (i.e. lower camelCase).
+:ballot_box_with_check: **YOU SHOULD** case all acronyms as though they were regular words (i.e. lower camelCase).
For example, `nextUrl` not `nextURL`.
-:ballot_box_with_check: **YOU SHOULD** use an "At" suffix in names of `date-time` values.
+:ballot_box_with_check: **YOU SHOULD** use an "At" suffix in names of `date-time` values.
For example, `createdAt` not `created` or `createdDateTime`.
-:ballot_box_with_check: **YOU SHOULD** use a suffix of the unit of measurement for values with a clear unit of measurement (such as bytes, miles, and so on). Use a generally accepted abbreviation for the units (e.g. "Km" rather than "Kilometers") when appropriate.
+:ballot_box_with_check: **YOU SHOULD** use a suffix of the unit of measurement for values with a clear unit of measurement (such as bytes, miles, and so on). Use a generally accepted abbreviation for the units (e.g. "Km" rather than "Kilometers") when appropriate.
-:ballot_box_with_check: **YOU SHOULD** use an int for time durations and include the time units in the name.
+:ballot_box_with_check: **YOU SHOULD** use an int for time durations and include the time units in the name.
For example, `expirationDays` as `int` and not `expiration` as `date-time`.
-:warning: **YOU SHOULD NOT** use brand names in resource or property names.
+:warning: **YOU SHOULD NOT** use brand names in resource or property names.
-:warning: **YOU SHOULD NOT** use acronyms or abbreviations unless they are broadly understood for example, "ID" or "URL", but not "Num" for "number".
+:warning: **YOU SHOULD NOT** use acronyms or abbreviations unless they are broadly understood for example, "ID" or "URL", but not "Num" for "number".
-:warning: **YOU SHOULD NOT** use names that are reserved words in widely used programming languages (including C#, Java, JavaScript/TypeScript, Python, C++, and Go).
+:warning: **YOU SHOULD NOT** use names that are reserved words in widely used programming languages (including C#, Java, JavaScript/TypeScript, Python, C++, and Go).
-:no_entry: **DO NOT** use "is" prefix in names of `boolean` values, e.g. "enabled" not "isEnabled".
+:no_entry: **DO NOT** use "is" prefix in names of `boolean` values, e.g. "enabled" not "isEnabled".
-:no_entry: **DO NOT** use redundant words in names.
+:no_entry: **DO NOT** use redundant words in names.
For example, `/phones/number` and not `phone/phoneNumber`.
@@ -152,22 +154,22 @@ The following are recommended names for properties that match the associated des
### `name` vs `id`
-:heavy_check_mark: **DO** use "Id" suffix for the name of the identifier of a resource.
+:white_check_mark: **DO** use "Id" suffix for the name of the identifier of a resource.
This holds even in the case where the identifier is assigned by the user with a PUT/PATCH method.
## Use Previews to Iterate
Before releasing your API plan to invest significant design effort, get customer feedback, & iterate through multiple preview releases. This is especially important for V1 as it establishes the abstractions and patterns that developers will use to interact with your service.
-:ballot_box_with_check: **YOU SHOULD** write and test hypotheses about how your customers will use the API.
+:ballot_box_with_check: **YOU SHOULD** write and test hypotheses about how your customers will use the API.
-:ballot_box_with_check: **YOU SHOULD** release and evaluate a minimum of 2 preview versions prior to the first GA release.
+:ballot_box_with_check: **YOU SHOULD** release and evaluate a minimum of 2 preview versions prior to the first GA release.
-:ballot_box_with_check: **YOU SHOULD** identify key scenarios or design decisions in your API that you want to test with customers, and ask customers for feedback and to share relevant code samples.
+:ballot_box_with_check: **YOU SHOULD** identify key scenarios or design decisions in your API that you want to test with customers, and ask customers for feedback and to share relevant code samples.
-:ballot_box_with_check: **YOU SHOULD** consider doing a _code with_ exercise in which you actively develop with the customer, observing and learning from their API usage.
+:ballot_box_with_check: **YOU SHOULD** consider doing a _code with_ exercise in which you actively develop with the customer, observing and learning from their API usage.
-:ballot_box_with_check: **YOU SHOULD** capture what you have learned during the preview stage and share these findings with your team and with the API Stewardship Board.
+:ballot_box_with_check: **YOU SHOULD** capture what you have learned during the preview stage and share these findings with your team and with the API Stewardship Board.
## Communicate Deprecations
As your service evolves over time, it will be natural that you want to remove operations that are no longer needed. For example, additional requirements or new capability in your service, may have resulted in a new operation that, effectively, replaces an old one.
@@ -186,12 +188,12 @@ Collections are another common area of friction for developers. It is important
An important consideration when defining a new service is support for pagination.
-:ballot_box_with_check: **YOU SHOULD** support server-side paging, even if your resource does not currently need paging. This avoids a breaking change when your service expands. See [Collections](./Guidelines.md#collections) for specific guidance.
+:ballot_box_with_check: **YOU SHOULD** support server-side paging, even if your resource does not currently need paging. This avoids a breaking change when your service expands. See [Collections](./Guidelines.md#collections) for specific guidance.
Another consideration for collections is support for sorting the set of returned items with the _orderby_ query parameter.
Sorting collection results can be extremely expensive for a service to implement as it must retrieve all items to sort them. And if the operation supports paging (which is likely), then a client request to get another page may have to retrieve all items and sort them again to determine which items are on the desired page.
-:heavy_check_mark: **YOU MAY** support `orderby` if customer scenarios really demand it and the service is confident that it can support it in perpetuity (even if the backing storage service changes someday).
+:heavy_check_mark: **YOU MAY** support `orderby` if customer scenarios really demand it and the service is confident that it can support it in perpetuity (even if the backing storage service changes someday).
Another important design pattern for avoiding surprises is idempotency. An operation is idempotent if it can be performed multiple times and have the same result as a single execution.
HTTP requires certain operations like GET, PUT, and DELETE to be idempotent, but for cloud services it is important to make _all_ operations idempotent so that clients can use retry in failure scenarios without risk of unintended consequences.
@@ -206,7 +208,7 @@ It is good practice to define the path for action operations that is easily dist
2) use a special character not in the set of valid characters for resource names to distinguish the "action" in the path.
In Azure we recommend distinguishing action operations by appending a ':' followed by an action verb to the final path segment. E.g.
-```http
+```text
https://...//:?
```
@@ -215,7 +217,7 @@ cannot collide with a resource path that contains user-specified resource ids.
## Long-Running Operations
-Long-running operations are an API design pattern that should be used when the processing of
+Long-running operations (LROs) are an API design pattern that should be used when the processing of
an operation may take a significant amount of time -- longer than a client will want to block
waiting for the result.
@@ -224,16 +226,95 @@ a _status monitor_, which is an ephemeral resource that will track the status an
The status monitor resource is distinct from the target resource (if any) and specific to the individual
operation request.
-A POST or DELETE operation returns a `202 Accepted` response with the status monitor in the response body.
-A long-running POST should not be used for resource create -- use PUT as described below.
-PATCH must never be used for long-running operations -- it should be reserved for simple resource updates.
-If a long-running update is required it should be implemented with POST.
+There are four types of LROs allowed in Azure REST APIs:
+
+1. An LRO to create or replace a resource that involves additional long-running processing.
+2. An LRO to delete a resource.
+3. An LRO to perform an action on or with an existing resource (or resource collection).
+4. An LRO to perform an action not related to an existing resource (or resource collection).
+
+The following sections describe these patterns in detail.
+
+### Create or replace a resource requiring additional long-running processing
+
+
+A special case of long-running operations that occurs often is a PUT operation to create or replace a resource
+that involves some additional long-running processing.
+One example is a resource that requires physical resources (e.g. servers) to be "provisioned" to make the resource functional.
+
+In this case:
+- The operation must use the PUT method (NOTE: PATCH is never allowed here)
+- The URL identifies the resource being created or replaced.
+- The request and response body have identical schemas & represent the resource.
+- The request may contain an `Operation-Id` header that the service will use as
+the ID of the status monitor created for the operation.
+- If the `Operation-Id` matches an existing operation and the request content is the same,
+treat as a retry and return the same response as the earlier request.
+Otherwise fail the request with a `409-Conflict`.
+
+```text
+PUT /items/FooBar&api-version=2022-05-01
+Operation-Id: 22
+
+{
+ "prop1": 555,
+ "prop2": "something"
+}
+```
+
+In this case the response to the initial request is a `201 Created` to indicate that
+the resource has been created or `200 OK` when the resource was replaced.
+The response body should be a representation of the resource that was created,
+and should include a `status` field indicating the current status of the resource.
+A status monitor is created to track the additional processing and the ID of the status monitor
+is returned in the `Operation-Id` header of the response.
+The response must also include an `Operation-Location` header for backward compatibility.
+If the resource supports ETags, the response may contain an `etag` header and possibly an `etag` property in the resource.
+
+```text
+HTTP/1.1 201 Created
+Operation-Id: 22
+Operation-Location: https://items/operations/22
+etag: "123abc"
+
+{
+ "id": "FooBar",
+ "status": "Provisioning",
+ "prop1": 555,
+ "prop2": "something",
+ "etag": "123abc"
+}
+```
+
+The client will issue a GET to the status monitor to obtain the status of the operation performing the additional processing.
+
+```text
+GET https://items/operations/22?api-version=2022-05-01
+```
+
+When the additional processing completes, the status monitor indicates if it succeeded or failed.
+
+```text
+HTTP/1.1 200 OK
-There is a special form of long-running operation initiated with PUT that is described
-in [Create (PUT) with additional long-running processing](./Guidelines.md#put-operation-with-additional-long-running-processing).
-The remainder of this section describes the pattern for long-running POST and DELETE operations.
+{
+ "id": "22",
+ "status": "Succeeded"
+}
+```
-This diagram illustrates how a long-running operation with a status monitor is initiated and then how the client
+If the additional processing failed, the service may delete the original resource if it is not usable in this state,
+but should clearly document this behavior.
+
+### Long-running delete operation
+
+A long-running delete operation returns a `202 Accepted` with a status monitor which the client uses to determine the outcome of the delete.
+
+The resource being deleted should remain visible (returned from a GET) until the delete operation completes successfully.
+
+When the delete operation completes successfully, a client must be able to create a new resource with the same name without conflicts.
+
+This diagram illustrates how a long-running DELETE operation is initiated and then how the client
determines it has completed and obtains its results:
```mermaid
@@ -241,7 +322,7 @@ sequenceDiagram
participant Client
participant API Endpoint
participant Status Monitor
- Client->>API Endpoint: POST/DELETE
+ Client->>API Endpoint: DELETE
API Endpoint->>Client: HTTP/1.1 202 Accepted { "id": "22", "status": "NotStarted" }
Client->>Status Monitor: GET
Status Monitor->>Client: HTTP/1.1 200 OK Retry-After: 5 { "id": "22", "status": "Running" }
@@ -249,8 +330,7 @@ sequenceDiagram
Status Monitor->>Client: HTTP/1.1 200 OK { "id": "22", "status": "Succeeded" }
```
-1. The client sends the request to initiate the long-running operation.
-The initial request could be a POST or DELETE method.
+1. The client sends the request to initiate the long-running DELETE operation.
The request may contain an `Operation-Id` header that the service uses as the ID of the status monitor created for the operation.
2. The service validates the request and initiates the operation processing.
@@ -259,8 +339,8 @@ Otherwise the service responds with a `202-Accepted` HTTP status code.
The response body is the status monitor for the operation including the ID, either from the request header or generated by the service.
When returning a status monitor whose status is not in a terminal state, the response must also include a `retry-after` header indicating the minimum number of seconds the client should wait
before polling (GETing) the status monitor URL again for an update.
-For backward compatibility, the response may also include an `Operation-Location` header containing the absolute URL
-of the status monitor resource (without an api-version query parameter).
+For backward compatibility, the response must also include an `Operation-Location` header containing the absolute URL
+of the status monitor resource, including an api-version query parameter.
3. After waiting at least the amount of time specified by the previous response's `Retry-after` header,
the client issues a GET request to the status monitor using the ID in the body of the initial response.
@@ -273,14 +353,11 @@ If the operation is still being processed, the status field will contain a "non-
5. After the operation processing completes, a GET request to the status monitor returns the status monitor with a status field set to a terminal value -- `Succeeded`, `Failed`, or `Canceled` -- that indicates the result of the operation.
If the status is `Failed`, the status monitor resource contains an `error` field with a `code` and `message` that describes the failure.
-If the status is `Succeeded` and the LRO is an Action operation, the operation results will be returned in the `result` field of the status monitor.
-If the status is `Succeeded` and the LRO is an operation on a resource, the client can perform a GET on the resource
-to observe the result of the operation if desired.
-6. There may be some cases where a long-running operation can be completed before the response to the initial request.
+6. There may be some cases where a long-running DELETE operation can be completed before the response to the initial request.
In these cases, the operation should still return a `202 Accepted` with the `status` property set to the appropriate terminal state.
-7. The service is responsible for purging the status-monitor resource.
+7. The service is responsible for purging the status monitor resource.
It should auto-purge the status monitor resource after completion (at least 24 hours).
The service may offer DELETE of the status monitor resource due to GDPR/privacy.
@@ -290,23 +367,26 @@ An action operation that is also long-running combines the [Action Operations](#
with the [Long Running Operations](#long-running-operations) pattern.
The operation is initiated with a POST operation and the operation path ends in `:`.
+A long-running POST should not be used for resource create: use PUT as described above.
+PATCH must never be used for long-running operations: it should be reserved for simple resource updates.
+If a long-running update is required it should be implemented with POST.
```text
POST /:?api-version=2022-05-01
-Operation-Id: 22
-
-{
- "arg1": 123
- "arg2": "abc"
-}
+Operation-Id: 22
+
+{
+ "arg1": 123
+ "arg2": "abc"
+}
```
-The response is a `202 Accepted` as described above.
+A long-running action operation returns a `202 Accepted` response with the status monitor in the response body.
```text
HTTP/1.1 202 Accepted
Operation-Location: https:///22
-
+
{
"id": "22",
"status": "NotStarted"
@@ -323,7 +403,7 @@ When the operation completes successfully, the result (if there is one) will be
```text
HTTP/1.1 200 OK
-
+
{
"id": "22",
"status": "Succeeded",
@@ -331,74 +411,87 @@ HTTP/1.1 200 OK
}
```
-### PUT with additional long-running processing
+This diagram illustrates how a long-running action operation is initiated and then how the client
+determines it has completed and obtains its results:
-A special case of long-running operation that occurs often is a PUT operation to create or replace a resource
-that involves some additional long-running processing.
-One example is a resource requires physical resources (e.g. servers) to be "provisioned" to make the resource functional.
-In this case, the request may contain an `Operation-Id` header that the service will use as
-the ID of the status monitor created for the operation.
+```mermaid
+sequenceDiagram
+ participant Client
+ participant API Endpoint
+ participant Status Monitor
+ Client->>API Endpoint: POST
+ API Endpoint->>Client: HTTP/1.1 202 Accepted { "id": "22", "status": "NotStarted" }
+ Client->>Status Monitor: GET
+ Status Monitor->>Client: HTTP/1.1 200 OK Retry-After: 5 { "id": "22", "status": "Running" }
+ Client->>Status Monitor: GET
+ Status Monitor->>Client: HTTP/1.1 200 OK { "id": "22", "status": "Succeeded", "result": { ... } }
+```
-```text
-PUT /items/FooBar&api-version=2022-05-01
-Operation-Id: 22
+1. The client sends the request to initiate the long-running action operation.
+The request may contain an `Operation-Id` header that the service uses as the ID of the status monitor created for the operation.
-{
- "prop1": 555,
- "prop2": "something"
-}
-```
+2. The service validates the request and initiates the operation processing.
+If there are any problems with the request, the service responds with a `4xx` status code and error response body.
+Otherwise the service responds with a `202-Accepted` HTTP status code.
+The response body is the status monitor for the operation including the ID, either from the request header or generated by the service.
+When returning a status monitor whose status is not in a terminal state, the response must also include a `retry-after` header indicating the minimum number of seconds the client should wait
+before polling (GETing) the status monitor URL again for an update.
+For backward compatibility, the response may also include an `Operation-Location` header containing the absolute URL
+of the status monitor resource, including an api-version query parameter.
-In this case the response to the initial request is a `201 Created` to indicate that the resource has been created
-or `200 OK` when the resource was replaced.
-The response body contains a representation of the created resource, which is the standard pattern for a create operation.
-A status monitor is created to track the additional processing and the ID of the status monitor
-is returned in the `Operation-Id` header of the response.
-The response may also include an `Operation-Location` header for backward compatibility.
-If the resource supports ETags, the response may contain an `etag` header and possibly an `etag` property in the resource.
+3. After waiting at least the amount of time specified by the previous response's `Retry-after` header,
+the client issues a GET request to the status monitor using the ID in the body of the initial response.
+The GET operation for the status monitor is documented in the REST API definition and the ID
+is the last URL path segment.
-```text
-HTTP/1.1 201 Created
-Operation-Id: 22
-Operation-Location: https://items/operations/22
-etag: "123abc"
+4. The status monitor responds with information about the operation including its current status,
+which should be represented as one of a fixed set of string values in a field named `status`.
+If the operation is still being processed, the status field will contain a "non-terminal" value, like `NotStarted` or `Running`.
-{
- "id": "FooBar",
- "etag": "123abc",
- "prop1": 555,
- "prop2": "something"
-}
-```
+5. After the operation processing completes, a GET request to the status monitor returns the status monitor with a status field set to a terminal value -- `Succeeded`, `Failed`, or `Canceled` -- that indicates the result of the operation.
+If the status is `Failed`, the status monitor resource contains an `error` field with a `code` and `message` that describes the failure.
+If the status is `Succeeded`, the operation results (if any) are returned in the `result` field of the status monitor.
-The client will issue a GET to the status monitor to obtain the status of the operation performing the additional processing.
+6. There may be some cases where a long-running action operation can be completed before the response to the initial request.
+In these cases, the operation should still return a `202 Accepted` with the `status` property set to the appropriate terminal state.
-```text
-GET https://items/operations/22?api-version=2022-05-01
-```
+7. The service is responsible for purging the status monitor resource.
+It should auto-purge the status monitor resource after completion (at least 24 hours).
+The service may offer DELETE of the status monitor resource due to GDPR/privacy.
-When the additional processing completes, the status monitor will indicate if it succeeded or failed.
+### Long-running action operation not related to a resource
-```text
-HTTP/1.1 200 OK
-
-{
- "id": "22",
- "status": "Succeeded"
-}
-```
+When a long-running action operation is not related to a specific resource (a batch operation is one example),
+another approach is needed.
-If the additional processing failed, the service may delete the original resource if it is not usable in this state,
-but would have to clearly document this behavior.
+This type of LRO should be initiated with a PUT method on a URL that represents the operation to be performed,
+and includes a final path parameter for the user-specified operation ID.
+The response of the PUT includes a response body containing a representation of the status monitor for the operation
+and an `Operation-Location` response header that contains the absolute URL of the status monitor.
+In this type of LRO, the status monitor should include any information from the request used to initiate the operation,
+so that a failed operation could be reissued if necessary.
-### Long-running delete operation
+Clients will use a GET on the status monitor URL to obtain the status and results of the operation.
+Since the HTTP semantic for PUT is to create a resource, the same schema should be used for the PUT request body,
+the PUT response body, and the response body of the GET for the status monitor for the operation.
+For this type of LRO, the status monitor URL should be the same URL as the PUT operation.
-A long-running delete operation follows the general pattern of a long-running operation --
-it returns a `202 Accepted` with a status monitor which the client uses to determine the outcome of the delete.
+The following examples illustrate this pattern.
-The resource being deleted should remain visible (returned from a GET) until the delete operation completes successfully.
+```text
+PUT /translate-operations/?api-version=2022-05-01
+
+
+```
+
+Note that the client specifies the operation id in the URL path.
-When the delete operation completes successfully, a client must be able to create new resource with same name without conflicts.
+A successful response to the PUT operation should have a `201 Created` status and response body
+that contains a representation of the status monitor _and_ any information from the request used to initiate the operation.
+
+The service is responsible for purging the status monitor after some period of time,
+but no earlier than 24 hours after the completion of the operation.
+The service may offer DELETE of the status monitor resource due to GDPR/privacy.
### Controlling a long-running operation
@@ -406,14 +499,14 @@ It might be necessary to support some control action on a long-running operation
This is implemented as a POST on the status monitor endpoint with `:` added.
```text
-POST /:cancel?api-version=2022-05-01
+POST /:cancel?api-version=2022-05-01
```
A successful response to a control operation should be a `200 OK` with a representation of the status monitor.
```text
-HTTP/1.1 200 OK
-
+HTTP/1.1 200 OK
+
{
"id": "22",
"status": "Canceled"
@@ -515,6 +608,61 @@ For example, the client can specify an `If-Match` header with the last ETag valu
The service processes the update only if the ETag value in the header matches the ETag of the current resource on the server.
By computing and returning ETags for your resources, you enable clients to avoid using a strategy where the "last write always wins."
+## Returning String Offsets & Lengths (Substrings)
+
+Some Azure services return substring offset & length values within a string. For example, the offset & length within a string to a name, email address, or phone number.
+When a service response includes a string, the client's programming language deserializes that string into that language's internal string encoding. Below are the possible encodings and examples of languages that use each encoding:
+
+| Encoding | Example languages |
+| -------- | ------- |
+| UTF-8 | Go, Rust, Ruby, PHP |
+| UTF-16 | JavaScript, Java, C# |
+| CodePoint (UTF-32) | Python |
+
+Because the service doesn't know in what language a client is written and what string encoding that language uses, the service can't return UTF-agnostic offset and length values that the client can use to index within the string. To address this, the service response must include offset & length values for all 3 possible encodings and then the client code must select the encoding required by its language's internal string encoding.
+
+For example, if a service response needed to identify offset & length values for "name" and "email" substrings, the JSON response would look like this:
+
+```text
+{
+ (... other properties not shown...)
+ "fullString": "(...some string containing a name and an email address...)",
+ "name": {
+ "offset": {
+ "utf8": 12,
+ "utf16": 10,
+ "codePoint": 4
+ },
+ "length": {
+ "uft8": 10,
+ "utf16": 8,
+ "codePoint": 2
+ }
+ },
+ "email": {
+ "offset": {
+ "utf8": 12,
+ "utf16": 10,
+ "codePoint": 4
+ },
+ "length": {
+ "uft8": 10,
+ "utf16": 8,
+ "codePoint": 4
+ }
+ }
+}
+```
+
+Then, the Go developer, for example, would get the substring containing the name using code like this:
+
+```go
+ var response := client.SomeMethodReturningJSONShownAbove(...)
+ name := response.fullString[ response.name.offset.utf8 : response.name.offset.utf8 + response.name.length.utf8]
+```
+
+The service must calculate the offset & length for all 3 encodings and return them because clients find it difficult working with Unicode encodings and how to convert from one encoding to another. In other words, we do this to simplify client development and ensure customer success when isolating a substring.
+
## Getting Help: The Azure REST API Stewardship Board
The Azure REST API Stewardship board is a collection of dedicated architects that are passionate about helping Azure service teams build interfaces that are intuitive, maintainable, consistent, and most importantly, delight our customers. Because APIs affect nearly all downstream decisions, you are encouraged to reach out to the Stewardship board early in the development process. These architects will work with you to apply these guidelines and identify any hidden pitfalls in your design.
diff --git a/azure/Guidelines.md b/azure/Guidelines.md
index ae15b2b3..dec9ef17 100644
--- a/azure/Guidelines.md
+++ b/azure/Guidelines.md
@@ -1,7 +1,7 @@
# Microsoft Azure REST API Guidelines
-
+
+
+:white_check_mark: **DO** use the following pattern when implementing an LRO action operating on an existing resource:
+
+```text
+POST /UrlToExistingResource:?api-version=&
+operation-id: `
+
+
+```
+
+The response must look like this:
+
+```text
+202 Accepted
+operation-id:
+operation-location: https://operations/
+
+
+```
+
+The request body contains information to be used to execute the action.
+
+For an idempotent POST (same `operation-id` and request body within some short time window), the service should return the same response as the initial request.
+
+For a non-idempotent POST, the service can treat the POST operation as idempotent (if performed within a short time window) or can treat the POST operation as initiating a brand new LRO action operation.
+
+:no_entry: **DO NOT** use a long-running POST to create a resource -- use PUT as described above.
+
+:white_check_mark: **DO** allow the client to pass an `Operation-Id` header with an ID for the operation's status monitor.
+
+:white_check_mark: **DO** generate an ID (typically a GUID) for the status monitor if the `Operation-Id` header was not passed by the client.
+
+:white_check_mark: **DO** fail a request with a `409-Conflict` if the `Operation-Id` header matches an existing operation unless the request is identical to the prior request (a retry scenario).
+
+:white_check_mark: **DO** return a `202-Accepted` status code from the request that initiates an LRO action on a resource if the processing of the operation was successfully initiated.
+
+:warning: **YOU SHOULD NOT** return any other `2xx` status code from the initial request of an LRO -- return `202-Accepted` and a status monitor even if processing was completed before the initiating request returns.
+
+:white_check_mark: **DO** return a status monitor in the response body as described in [Obtaining status and results of long-running operations](#obtaining-status-and-results-of-long-running-operations).
+
+#### LRO action with no related resource pattern
-**OperationStatus** : Object
+:white_check_mark: **DO** use the following pattern when implementing an LRO action not related to a specific resource (such as a batch operation):
+
+```text
+PUT /?api-version=
+
+>
+```
+
+The response must look like this:
+
+```text
+201 Created
+operation-location:
+
+
+```
+
+:ballot_box_with_check: **YOU SHOULD**
+define a unique operation endpoint for each LRO action with no related resource.
+
+:white_check_mark: **DO** require the
+`Operation-Id` as the final path segment in the URL.
+
+Note: The `operation-id` URL segment (not header) is *required*, forcing the client to specify the status monitor's resource ID
+and is also used for retries/idempotency.
+
+:white_check_mark: **DO** return a `201 Created` status code
+with an `operation-location` response header if the LRO Action operation was accepted for processing.
+
+:white_check_mark: **DO** return a
+status monitor in the response body that contains the operation status, request parameters, and when the operation completes either
+the operation result or error.
+
+Note: Since all request parameters must be present in the status monitor,
+the request and response body of the PUT can be defined with a single schema.
+
+:ballot_box_with_check: **YOU SHOULD**
+return the status monitor for an operation for a subsequent GET on the URL that initiates the LRO, and use this endpoint as
+the status monitor URL returned in the `operation-location` response header.
+
+#### The Status Monitor Resource
+
+All patterns that initiate a LRO either implicitly or explicitly create a [Status Monitor resource](https://datatracker.ietf.org/doc/html/rfc7231#section-6.3.3) in the service's `operations` collection.
+
+:white_check_mark: **DO** return a status monitor in the response body that conforms with the following structure:
Property | Type | Required | Description
-------- | ----------- | :------: | -----------
`id` | string | true | The unique id of the operation
-`status` | string | true | enum that includes values "NotStarted", "Running", "Succeeded", "Failed", and "Canceled"
-`error` | ErrorDetail | | Error object that describes the error when status is "Failed"
-`result` | object | | Only for POST action-type LRO, the results of the operation when completed successfully
-additional properties | | | Additional named or dynamic properties of the operation
+`kind` | string enum | true(*) | The kind of operation
+`status` | string enum | true | The operation's current status: "NotStarted", "Running", "Succeeded", "Failed", and "Canceled"
+`error` | ErrorDetail | | If `status`=="Failed", contains reason for failure
+`result` | object | | If `status`=="Succeeded" && Action LRO (POST or PUT), contains success result if needed
+additional properties | | | Additional named or dynamic properties of the operation
-:white_check_mark: **DO** include the `id` of the operation and any other values needed for the client to form a GET request to the status monitor (e.g. a `location` path parameter).
+(*): When a status monitor endpoint supports multiple operations with different result structures or additional properties,
+the status monitor **must** be polymorphic -- it **must** contain a required `kind` property that indicates the kind of long-running operation.
-:white_check_mark: **DO** include a `Retry-After` header in the response to GET requests to the status monitor if the operation is not complete. The value of this header should be an integer number of seconds to wait before making the next request to the status monitor.
+#### Obtaining status and results of long-running operations
+
+:white_check_mark: **DO** use the following pattern to allow clients to poll the current state of a Status Monitor resource:
+
+```text
+GET /?api-version=
+```
+
+The response must look like this:
+
+```text
+200 OK
+retry-after: (if status not terminal)
+
+
+```
+
+:white_check_mark: **DO** support the GET method on the status monitor endpoint that returns a `200-OK` response with the current state of the status monitor.
+
+:ballot_box_with_check: **YOU SHOULD** allow any valid value of the `api-version` query parameter to be used in the GET operation on the status monitor.
+
+- Note: Clients may replace the value of `api-version` in the `operation-location` URL with a value appropriate for their application. Remember that the client initiating the LRO may not be the same client polling the LRO's status.
+
+:white_check_mark: **DO** include the `id` of the operation and any other values needed for the client to form a GET request to the status monitor (e.g. a `location` path parameter).
:white_check_mark: **DO** include the `result` property (if any) in the status monitor for a POST action-type long-running operation when the operation completes successfully.
-:no_entry: **DO NOT** include a `result` property in the status monitor for a long-running operation that is not a POST action-type long-running operation.
+:no_entry: **DO NOT** include a `result` property in the status monitor for a long-running operation that is not an action-type long-running operation.
+
+:white_check_mark: **DO** include a `retry-after` header in the response if the operation is not complete. The value of this header should be an integer number of seconds that the client should wait before polling the status monitor again.
:white_check_mark: **DO** retain the status monitor resource for some publicly documented period of time (at least 24 hours) after the operation completes.
+#### Pattern to List Status Monitors
+
+Use the following patterns to allow clients to list Status Monitor resources.
+
+:ballot_box_with_check:
+**YOU MAY** support a GET method on any status monitor collection URL that returns a list of the status monitors in that collection.
+
+:ballot_box_with_check:
+**YOU SHOULD** support a list operation for any status monitor collection that includes status monitors for LRO Actions with no related resource.
+
+:ballot_box_with_check:
+**YOU SHOULD** support the `filter` query parameter on the list operation for any polymorphic status monitor collection and support filtering on the `kind` value of the status monitor.
+
+For example, the following request should return all status monitor resources whose `kind` is either "VMInitializing" *or* "VMRebooting"
+and whose status is "NotStarted" *or* "Succeeded".
+
+```text
+GET /operations?filter=(kind eq 'VMInitializing' or kind eq 'VMRebooting') and (status eq 'NotStarted' or status eq 'Succeeded')
+```
+
### Bring your own Storage (BYOS)
+
Many services need to store and retrieve data files. For this scenario, the service should not implement its own
storage APIs and should instead leverage the existing Azure Storage service. When doing this, the customer
"owns" the storage account and just tells your service to use it. Colloquially, we call this Bring Your Own Storage as the customer is bringing their storage account to another service. BYOS provides significant benefits to service implementors: security, performance, uptime, etc. And, of course, most Azure customers are already familiar with the Azure Storage service.
@@ -951,7 +1109,7 @@ While Azure Managed Storage may be easier to get started with, as your service e
:white_check_mark: **DO** use the Bring Your Own Storage pattern.
-:white_check_mark: **DO** use a blob prefix for a logical folder (avoid terms such as ```directory```, ```folder```, or ```path```).
+:white_check_mark: **DO** use a blob prefix for a logical folder (avoid terms such as `directory`, `folder`, or `path`).
:no_entry: **DO NOT** require a fresh container per operation.
@@ -1092,8 +1250,28 @@ While it may be tempting to use a revision/version number for the resource as th
:white_check_mark: **DO**, when supporting multiple representations (e.g. Content-Encodings) for the same resource, generate different ETag values for the different representations.
+
+### Returning String Offsets & Lengths (Substrings)
+
+All string values in JSON are inherently Unicode and UTF-8 encoded, but clients written in a high-level programming language must work with strings in that language's string encoding, which may be UTF-8, UTF-16, or CodePoints (UTF-32).
+When a service response includes a string offset or length value, it should specify these values in all 3 encodings to simplify client development and ensure customer success when isolating a substring.
+See the [Returning String Offsets & Lengths] section in Considerations for Service Design for more detail, including an example JSON response containing string offset and length fields.
+
+[Returning String Offsets & Lengths]: https://github.com/microsoft/api-guidelines/blob/vNext/azure/ConsiderationsForServiceDesign.md#returning-string-offsets--lengths-substrings
+
+:white_check_mark: **DO** include all 3 encodings (UTF-8, UTF-16, and CodePoint) for every string offset or length value in a service response.
+
+:white_check_mark: **DO** define every string offset or length value in a service response as an object with the following structure:
+
+| Property | Type | Required | Description |
+| ----------- | ------- | :------: | ----------- |
+| `utf8` | integer | true | The offset or length of the substring in UTF-8 encoding |
+| `utf16` | integer | true | The offset or length of the substring in UTF-16 encoding |
+| `codePoint` | integer | true | The offset or length of the substring in CodePoint encoding |
+
### Distributed Tracing & Telemetry
+
Azure SDK client guidelines specify that client libraries must send telemetry data through the `User-Agent` header, `X-MS-UserAgent` header, and Open Telemetry.
Client libraries are required to send telemetry and distributed tracing information on every request. Telemetry information is vital to the effective operation of your service and should be a consideration from the outset of design and implementation efforts.
diff --git a/graph/Guidelines-deprecated.md b/graph/Guidelines-deprecated.md
new file mode 100644
index 00000000..9bf636cc
--- /dev/null
+++ b/graph/Guidelines-deprecated.md
@@ -0,0 +1,2450 @@
+
+> # DEPRECATION NOTICE TO READERS
+>
+> This document is being deprecated and merged with the [Microsoft Graph REST API Guidelines](GuidelinesGraph.md), with a removal date of July 1, 2024. Please refer to the notes below for the latest guidance.
+>
+> ## **Guidance for Microsoft Graph service teams**
+>
+> Graph service teams should reference the companion document, [Microsoft Graph REST API Guidelines](GuidelinesGraph.md) when building or modifying their services. This document and the associated pattern catalog provides a refined set of guidance targeted specifically for Microsoft Graph services.
+>
+---
+# Microsoft REST API Guidelines
+
+This are Microsoft's internal company-wide REST API design guidelines.
+Teams at Microsoft typically reference this document when setting API design policy.
+They may additionally create documents specific to their team, adding further guidance or making adjustments as appropriate to their circumstances.
+
+## Microsoft REST API Guidelines Working Group
+
+Name | Name | Name |
+---------------------------- | -------------------------------------- | ----------------------------------------
+Dave Campbell (CTO C+E) | Rick Rashid (CTO ASG) | John Shewchuk (Technical Fellow, TED HQ)
+Mark Russinovich (CTO Azure) | Steve Lucco (Technical Fellow, DevDiv) | Murali Krishnaprasad (Azure App Plat)
+Rob Howard (ASG) | Peter Torr (OSG) | Chris Mullins (ASG)
+
+
+Document editors: John Gossman (C+E), Chris Mullins (ASG), Gareth Jones (ASG), Rob Dolin (C+E), Mark Stafford (C+E)
+
+
+# Microsoft REST API Guidelines
+
+## 1. Abstract
+The Microsoft REST API Guidelines, as a design principle, encourages application developers to have resources accessible to them via a RESTful HTTP interface.
+To provide the smoothest possible experience for developers on platforms following the Microsoft REST API Guidelines, REST APIs SHOULD follow consistent design guidelines to make using them easy and intuitive.
+
+This document establishes the guidelines Microsoft REST APIs SHOULD follow so RESTful interfaces are developed consistently.
+
+## 2. Table of contents
+
+
+- [Microsoft REST API Guidelines](#microsoft-rest-api-guidelines)
+ - [Microsoft REST API Guidelines Working Group](#microsoft-rest-api-guidelines-working-group)
+- [Microsoft REST API Guidelines](#microsoft-rest-api-guidelines-1)
+ - [1. Abstract](#1-abstract)
+ - [2. Table of contents](#2-table-of-contents)
+ - [3. Introduction](#3-introduction)
+ - [3.1. Recommended reading](#31-recommended-reading)
+ - [4. Interpreting the guidelines](#4-interpreting-the-guidelines)
+ - [4.1. Application of the guidelines](#41-application-of-the-guidelines)
+ - [4.2. Guidelines for existing services and versioning of services](#42-guidelines-for-existing-services-and-versioning-of-services)
+ - [4.3. Requirements language](#43-requirements-language)
+ - [4.4. License](#44-license)
+ - [5. Taxonomy](#5-taxonomy)
+ - [5.1. Errors](#51-errors)
+ - [5.2. Faults](#52-faults)
+ - [5.3. Latency](#53-latency)
+ - [5.4. Time to complete](#54-time-to-complete)
+ - [5.5. Long running API faults](#55-long-running-api-faults)
+ - [6. Client guidance](#6-client-guidance)
+ - [6.1. Ignore rule](#61-ignore-rule)
+ - [6.2. Variable order rule](#62-variable-order-rule)
+ - [6.3. Silent fail rule](#63-silent-fail-rule)
+ - [7. Consistency fundamentals](#7-consistency-fundamentals)
+ - [7.1. URL structure](#71-url-structure)
+ - [7.2. URL length](#72-url-length)
+ - [7.3. Canonical identifier](#73-canonical-identifier)
+ - [7.4. Supported methods](#74-supported-methods)
+ - [7.4.1. POST](#741-post)
+ - [7.4.2. PATCH](#742-patch)
+ - [7.4.3. Creating resources via PATCH (UPSERT semantics)](#743-creating-resources-via-patch-upsert-semantics)
+ - [7.4.4. Options and link headers](#744-options-and-link-headers)
+ - [7.5. Standard request headers](#75-standard-request-headers)
+ - [7.6. Standard response headers](#76-standard-response-headers)
+ - [7.7. Custom headers](#77-custom-headers)
+ - [7.8. Specifying headers as query parameters](#78-specifying-headers-as-query-parameters)
+ - [7.9. PII parameters](#79-pii-parameters)
+ - [7.10. Response formats](#710-response-formats)
+ - [7.10.1. Clients-specified response format](#7101-clients-specified-response-format)
+ - [7.10.2. Error condition responses](#7102-error-condition-responses)
+ - [ErrorResponse : Object](#errorresponse--object)
+ - [Error : Object](#error--object)
+ - [InnerError : Object](#innererror--object)
+ - [Examples](#examples)
+ - [7.11. HTTP Status Codes](#711-http-status-codes)
+ - [7.12. Client library optional](#712-client-library-optional)
+ - [8. CORS](#8-cors)
+ - [8.1. Client guidance](#81-client-guidance)
+ - [8.1.1. Avoiding preflight](#811-avoiding-preflight)
+ - [8.2. Service guidance](#82-service-guidance)
+ - [9. Collections](#9-collections)
+ - [9.1. Item keys](#91-item-keys)
+ - [9.2. Serialization](#92-serialization)
+ - [9.3. Collection URL patterns](#93-collection-url-patterns)
+ - [9.3.1. Nested collections and properties](#931-nested-collections-and-properties)
+ - [9.4. Big collections](#94-big-collections)
+ - [9.5. Changing collections](#95-changing-collections)
+ - [9.6. Sorting collections](#96-sorting-collections)
+ - [9.6.1. Interpreting a sorting expression](#961-interpreting-a-sorting-expression)
+ - [9.7. Filtering](#97-filtering)
+ - [9.7.1. Filter operations](#971-filter-operations)
+ - [9.7.2. Operator examples](#972-operator-examples)
+ - [9.7.3. Operator precedence](#973-operator-precedence)
+ - [9.8. Pagination](#98-pagination)
+ - [9.8.1. Server-driven paging](#981-server-driven-paging)
+ - [9.8.2. Client-driven paging](#982-client-driven-paging)
+ - [9.8.3. Additional considerations](#983-additional-considerations)
+ - [9.9. Compound collection operations](#99-compound-collection-operations)
+ - [9.10. Empty Results](#910-empty-results)
+ - [10. Delta queries](#10-delta-queries)
+ - [10.1. Delta links](#101-delta-links)
+ - [10.2. Entity representation](#102-entity-representation)
+ - [10.3. Obtaining a delta link](#103-obtaining-a-delta-link)
+ - [10.4. Contents of a delta link response](#104-contents-of-a-delta-link-response)
+ - [10.5. Using a delta link](#105-using-a-delta-link)
+ - [11. JSON standardizations](#11-json-standardizations)
+ - [11.1. JSON formatting standardization for primitive types](#111-json-formatting-standardization-for-primitive-types)
+ - [11.2. Guidelines for dates and times](#112-guidelines-for-dates-and-times)
+ - [11.2.1. Producing dates](#1121-producing-dates)
+ - [11.2.2. Consuming dates](#1122-consuming-dates)
+ - [11.2.3. Compatibility](#1123-compatibility)
+ - [11.3. JSON serialization of dates and times](#113-json-serialization-of-dates-and-times)
+ - [11.3.1. The `DateLiteral` format](#1131-the-dateliteral-format)
+ - [11.3.2. Commentary on date formatting](#1132-commentary-on-date-formatting)
+ - [11.4. Durations](#114-durations)
+ - [11.5. Intervals](#115-intervals)
+ - [11.6. Repeating intervals](#116-repeating-intervals)
+ - [12. Versioning](#12-versioning)
+ - [12.1. Versioning formats](#121-versioning-formats)
+ - [12.1.1. Group versioning](#1211-group-versioning)
+ - [Examples of group versioning](#examples-of-group-versioning)
+ - [12.2. When to version](#122-when-to-version)
+ - [12.3. Definition of a breaking change](#123-definition-of-a-breaking-change)
+ - [13. Long running operations](#13-long-running-operations)
+ - [13.1. Resource based long running operations (RELO)](#131-resource-based-long-running-operations-relo)
+ - [13.2. Stepwise long running operations](#132-stepwise-long-running-operations)
+ - [13.2.1. PUT](#1321-put)
+ - [13.2.2. POST](#1322-post)
+ - [13.2.3. POST, hybrid model](#1323-post-hybrid-model)
+ - [13.2.4. Operations resource](#1324-operations-resource)
+ - [13.2.5. Operation resource](#1325-operation-resource)
+ - [Percent complete](#percent-complete)
+ - [Target resource location](#target-resource-location)
+ - [13.2.6. Operation tombstones](#1326-operation-tombstones)
+ - [13.2.7. The typical flow, polling](#1327-the-typical-flow-polling)
+ - [Example of the typical flow, polling](#example-of-the-typical-flow-polling)
+ - [13.2.8. The typical flow, push notifications](#1328-the-typical-flow-push-notifications)
+ - [Example of the typical flow, push notifications existing subscription](#example-of-the-typical-flow-push-notifications-existing-subscription)
+ - [13.2.9. Retry-After](#1329-retry-after)
+ - [13.3. Retention policy for operation results](#133-retention-policy-for-operation-results)
+ - [14. Throttling, Quotas, and Limits](#14-throttling-quotas-and-limits)
+ - [14.1. Principles](#141-principles)
+ - [14.2. Return Codes (429 vs 503)](#142-return-codes-429-vs-503)
+ - [14.3. Retry-After and RateLimit Headers](#143-retry-after-and-ratelimit-headers)
+ - [14.4. Service Guidance](#144-service-guidance)
+ - [14.4.1. Responsiveness](#1441-responsiveness)
+ - [14.4.2. Rate Limits and Quotas](#1442-rate-limits-and-quotas)
+ - [14.4.3. Overloaded services](#1443-overloaded-services)
+ - [14.4.4. Example Response](#1444-example-response)
+ - [14.5. Caller Guidance](#145-caller-guidance)
+ - [14.6. Handling callers that ignore Retry-After headers](#146-handling-callers-that-ignore-retry-after-headers)
+ - [15. Push notifications via webhooks](#15-push-notifications-via-webhooks)
+ - [15.1. Scope](#151-scope)
+ - [15.2. Principles](#152-principles)
+ - [15.3. Types of subscriptions](#153-types-of-subscriptions)
+ - [15.4. Call sequences](#154-call-sequences)
+ - [15.5. Verifying subscriptions](#155-verifying-subscriptions)
+ - [15.6. Receiving notifications](#156-receiving-notifications)
+ - [15.6.1. Notification payload](#1561-notification-payload)
+ - [15.7. Managing subscriptions programmatically](#157-managing-subscriptions-programmatically)
+ - [15.7.1. Creating subscriptions](#1571-creating-subscriptions)
+ - [15.7.2. Updating subscriptions](#1572-updating-subscriptions)
+ - [15.7.3. Deleting subscriptions](#1573-deleting-subscriptions)
+ - [15.7.4. Enumerating subscriptions](#1574-enumerating-subscriptions)
+ - [15.8. Security](#158-security)
+ - [16. Unsupported requests](#16-unsupported-requests)
+ - [16.1. Essential guidance](#161-essential-guidance)
+ - [16.2. Feature allow list](#162-feature-allow-list)
+ - [16.2.1. Error response](#1621-error-response)
+ - [17. Naming guidelines](#17-naming-guidelines)
+ - [17.1. Approach](#171-approach)
+ - [17.2. Casing](#172-casing)
+ - [17.3. Names to avoid](#173-names-to-avoid)
+ - [17.4. Forming compound names](#174-forming-compound-names)
+ - [17.5. Identity properties](#175-identity-properties)
+ - [17.6. Date and time properties](#176-date-and-time-properties)
+ - [17.7. Name properties](#177-name-properties)
+ - [17.8. Collections and counts](#178-collections-and-counts)
+ - [17.9. Common property names](#179-common-property-names)
+ - [18. Appendix](#18-appendix)
+ - [18.1. Sequence diagram notes](#181-sequence-diagram-notes)
+ - [18.1.1. Push notifications, per user flow](#1811-push-notifications-per-user-flow)
+ - [18.1.2. Push notifications, firehose flow](#1812-push-notifications-firehose-flow)
+
+
+
+## 3. Introduction
+Developers access most Microsoft Cloud Platform resources via HTTP interfaces.
+Although each service typically provides language-specific frameworks to wrap their APIs, all of their operations eventually boil down to HTTP requests.
+Microsoft must support a wide range of clients and services and cannot rely on rich frameworks being available for every development environment.
+Thus, a goal of these guidelines is to ensure Microsoft REST APIs can be easily and consistently consumed by any client with basic HTTP support.
+
+To provide the smoothest possible experience for developers, it's important to have these APIs follow consistent design guidelines, thus making using them easy and intuitive.
+This document establishes the guidelines to be followed by Microsoft REST API developers for developing such APIs consistently.
+
+The benefits of consistency accrue in aggregate as well; consistency allows teams to leverage common code, patterns, documentation and design decisions.
+
+These guidelines aim to achieve the following:
+- Define consistent practices and patterns for all API endpoints across Microsoft.
+- Adhere as closely as possible to accepted REST/HTTP best practices in the industry at-large. [\*]
+- Make accessing Microsoft Services via REST interfaces easy for all application developers.
+- Allow service developers to leverage the prior work of other services to implement, test and document REST endpoints defined consistently.
+- Allow for partners (e.g., non-Microsoft entities) to use these guidelines for their own REST endpoint design.
+
+[\*] Note: The guidelines are designed to align with building services which comply with the REST architectural style, though they do not address or require building services that follow the REST constraints.
+The term "REST" is used throughout this document to mean services that are in the spirit of REST rather than adhering to REST by the book.*
+
+### 3.1. Recommended reading
+Understanding the philosophy behind the REST Architectural Style is recommended for developing good HTTP-based services.
+If you are new to RESTful design, here are some good resources:
+
+[REST on Wikipedia][rest-on-wikipedia] -- Overview of common definitions and core ideas behind REST.
+
+[REST Dissertation][fielding] -- The chapter on REST in Roy Fielding's dissertation on Network Architecture, "Architectural Styles and the Design of Network-based Software Architectures"
+
+[RFC 7231][rfc-7231] -- Defines the specification for HTTP/1.1 semantics, and is considered the authoritative resource.
+
+[REST in Practice][rest-in-practice] -- Book on the fundamentals of REST.
+
+## 4. Interpreting the guidelines
+### 4.1. Application of the guidelines
+These guidelines are applicable to any REST API exposed publicly by Microsoft or any partner service.
+Private or internal APIs SHOULD also try to follow these guidelines because internal services tend to eventually be exposed publicly.
+ Consistency is valuable to not only external customers but also internal service consumers, and these guidelines offer best practices useful for any service.
+
+There are legitimate reasons for exemption from these guidelines.
+Obviously, a REST service that implements or must interoperate with some externally defined REST API must be compatible with that API and not necessarily these guidelines.
+Some services MAY also have special performance needs that require a different format, such as a binary protocol.
+
+### 4.2. Guidelines for existing services and versioning of services
+We do not recommend making a breaking change to a service that predates these guidelines simply for the sake of compliance.
+The service SHOULD try to become compliant at the next version release when compatibility is being broken anyway.
+When a service adds a new API, that API SHOULD be consistent with the other APIs of the same version.
+So if a service was written against version 1.0 of the guidelines, new APIs added incrementally to the service SHOULD also follow version 1.0. The service can then upgrade to align with the latest version of the guidelines at the service's next major release.
+
+### 4.3. Requirements language
+The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119][rfc-2119].
+
+### 4.4. License
+
+This work is licensed under the Creative Commons Attribution 4.0 International License.
+To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.
+
+## 5. Taxonomy
+As part of onboarding to Microsoft REST API Guidelines, services MUST comply with the taxonomy defined below.
+
+### 5.1. Errors
+Errors, or more specifically Service Errors, are defined as a client passing invalid data to the service and the service _correctly_ rejecting that data.
+Examples include invalid credentials, incorrect parameters, unknown version IDs, or similar.
+These are generally "4xx" HTTP error codes and are the result of a client passing incorrect or invalid data.
+
+Errors do _not_ contribute to overall API availability.
+
+### 5.2. Faults
+Faults, or more specifically Service Faults, are defined as the service failing to correctly return in response to a valid client request.
+These are generally "5xx" HTTP error codes.
+
+Faults _do_ contribute to the overall API availability.
+
+Calls that fail due to rate limiting or quota failures MUST NOT count as faults.
+Calls that fail as the result of a service fast-failing requests (often for its own protection) do count as faults.
+
+### 5.3. Latency
+Latency is defined as how long a particular API call takes to complete, measured as closely to the client as possible.
+This metric applies to both synchronous and asynchronous APIs in the same way.
+For long running calls, the latency is measured on the initial request and measures how long that call (not the overall operation) takes to complete.
+
+### 5.4. Time to complete
+Services that expose long operations MUST track "Time to Complete" metrics around those operations.
+
+### 5.5. Long running API faults
+For a Long Running API, it's possible for both the initial request which begins the operation and the request which retrieves the results to technically work (each passing back a 200) but for the underlying operation to have failed.
+Long Running faults MUST roll up as faults into the overall Availability metrics.
+
+## 6. Client guidance
+To ensure the best possible experience for clients talking to a REST service, clients SHOULD adhere to the following best practices:
+
+### 6.1. Ignore rule
+For loosely coupled clients where the exact shape of the data is not known before the call, if the server returns something the client wasn't expecting, the client MUST safely ignore it.
+
+Some services MAY add fields to responses without changing versions numbers.
+Services that do so MUST make this clear in their documentation and clients MUST ignore unknown fields.
+
+### 6.2. Variable order rule
+Clients MUST NOT rely on the order in which data appears in JSON service responses.
+For example, clients SHOULD be resilient to the reordering of fields within a JSON object.
+When supported by the service, clients MAY request that data be returned in a specific order.
+For example, services MAY support the use of the _$orderBy_ querystring parameter to specify the order of elements within a JSON array.
+Services MAY also explicitly specify the ordering of some elements as part of the service contract.
+For example, a service MAY always return a JSON object's "type" information as the first field in an object to simplify response parsing on the client.
+Clients MAY rely on ordering behavior explicitly identified by the service.
+
+### 6.3. Silent fail rule
+Clients requesting OPTIONAL server functionality (such as optional headers) MUST be resilient to the server ignoring that particular functionality.
+
+## 7. Consistency fundamentals
+### 7.1. URL structure
+Humans SHOULD be able to easily read and construct URLs.
+
+This facilitates discovery and eases adoption on platforms without a well-supported client library.
+
+An example of a well-structured URL is:
+
+```
+https://api.contoso.com/v1.0/people/jdoe@contoso.com/inbox
+```
+
+An example URL that is not friendly is:
+
+```
+https://api.contoso.com/EWS/OData/Users('jdoe@microsoft.com')/Folders('AAMkADdiYzI1MjUzLTk4MjQtNDQ1Yy05YjJkLWNlMzMzYmIzNTY0MwAuAAAAAACzMsPHYH6HQoSwfdpDx-2bAQCXhUk6PC1dS7AERFluCgBfAAABo58UAAA=')
+```
+
+A frequent pattern that comes up is the use of URLs as values.
+Services MAY use URLs as values.
+For example, the following is acceptable:
+
+```
+https://api.contoso.com/v1.0/items?url=https://resources.contoso.com/shoes/fancy
+```
+
+### 7.2. URL length
+The HTTP 1.1 message format, defined in RFC 7230, in section [3.1.1][rfc-7230-3-1-1], defines no length limit on the Request Line, which includes the target URL.
+From the RFC:
+
+> HTTP does not place a predefined limit on the length of a
+ request-line. [...] A server that receives a request-target longer than any URI it wishes to parse MUST respond
+ with a 414 (URI Too Long) status code.
+
+Services that can generate URLs longer than 2,083 characters MUST make accommodations for the clients they wish to support.
+Here are some sources for determining what target clients support:
+
+ * [https://stackoverflow.com/a/417184](https://stackoverflow.com/a/417184)
+ * [https://blogs.msdn.microsoft.com/ieinternals/2014/08/13/url-length-limits/](https://blogs.msdn.microsoft.com/ieinternals/2014/08/13/url-length-limits/)
+
+Also note that some technology stacks have hard and adjustable URL limits, so keep this in mind as you design your services.
+
+### 7.3. Canonical identifier
+In addition to friendly URLs, resources that can be moved or be renamed SHOULD expose a URL that contains a unique stable identifier.
+It MAY be necessary to interact with the service to obtain a stable URL from the friendly name for the resource, as in the case of the "/my" shortcut used by some services.
+
+The stable identifier is not required to be a GUID.
+
+An example of a URL containing a canonical identifier is:
+
+```
+https://api.contoso.com/v1.0/people/7011042402/inbox
+```
+
+### 7.4. Supported methods
+Operations MUST use the proper HTTP methods whenever possible, and operation idempotency MUST be respected.
+HTTP methods are frequently referred to as the HTTP verbs.
+The terms are synonymous in this context, however the HTTP specification uses the term method.
+
+Below is a list of methods that Microsoft REST services SHOULD support.
+Not all resources will support all methods, but all resources using the methods below MUST conform to their usage.
+
+Method | Description | Is Idempotent
+------- | -------------------------------------------------------------------------------------------------------------------------- | -------------
+GET | Return the current value of an object | True
+PUT | Replace an object, or create a named object, when applicable | True
+DELETE | Delete an object | True
+POST | Create a new object based on the data provided, or submit a command | False
+HEAD | Return metadata of an object for a GET response. Resources that support the GET method MAY support the HEAD method as well | True
+PATCH | Apply a partial update to an object | False
+OPTIONS | Get information about a request; see below for details. | True
+
+Table 1
+
+#### 7.4.1. POST
+POST operations SHOULD support the Location response header to specify the location of any created resource that was not explicitly named, via the Location header.
+
+As an example, imagine a service that allows creation of hosted servers, which will be named by the service:
+
+```http
+POST http://api.contoso.com/account1/servers
+```
+
+The response would be something like:
+
+```http
+201 Created
+Location: http://api.contoso.com/account1/servers/server321
+```
+
+Where "server321" is the service-allocated server name.
+
+Services MAY also return the full metadata for the created item in the response.
+
+#### 7.4.2. PATCH
+PATCH has been standardized by IETF as the method to be used for updating an existing object incrementally (see [RFC 5789][rfc-5789]).
+Microsoft REST API Guidelines compliant APIs SHOULD support PATCH.
+
+#### 7.4.3. Creating resources via PATCH (UPSERT semantics)
+Services that allow callers to specify key values on create SHOULD support UPSERT semantics, and those that do MUST support creating resources using PATCH.
+Because PUT is defined as a complete replacement of the content, it is dangerous for clients to use PUT to modify data.
+Clients that do not understand (and hence ignore) properties on a resource are not likely to provide them on a PUT when trying to update a resource, hence such properties could be inadvertently removed.
+Services MAY optionally support PUT to update existing resources, but if they do they MUST use replacement semantics (that is, after the PUT, the resource's properties MUST match what was provided in the request, including deleting any server properties that were not provided).
+
+Under UPSERT semantics, a PATCH call to a nonexistent resource is handled by the server as a "create", and a PATCH call to an existing resource is handled as an "update". To ensure that an update request is not treated as a create or vice versa, the client MAY specify precondition HTTP headers in the request.
+The service MUST NOT treat a PATCH request as an insert if it contains an If-Match header and MUST NOT treat a PATCH request as an update if it contains an If-None-Match header with a value of "*".
+
+If a service does not support UPSERT, then a PATCH call against a resource that does not exist MUST result in an HTTP "409 Conflict" error.
+
+#### 7.4.4. Options and link headers
+OPTIONS allows a client to retrieve information about a resource, at a minimum by returning the Allow header denoting the valid methods for this resource.
+
+In addition, services SHOULD include a Link header (see [RFC 5988][rfc-5988]) to point to documentation for the resource in question:
+
+```http
+Link: <{help}>; rel="help"
+```
+
+Where {help} is the URL to a documentation resource.
+
+For examples on use of OPTIONS, see [preflighting CORS cross-domain calls][cors-preflight].
+
+### 7.5. Standard request headers
+The table of request headers below SHOULD be used by Microsoft REST API Guidelines services.
+Using these headers is not mandated, but if used they MUST be used consistently.
+
+All header values MUST follow the syntax rules set forth in the specification where the header field is defined.
+Many HTTP headers are defined in [RFC7231][rfc-7231], however a complete list of approved headers can be found in the [IANA Header Registry][IANA-headers]."
+
+Header | Type | Description
+--------------------------------- | ------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+Authorization | String | Authorization header for the request
+Date | Date | Timestamp of the request, based on the client's clock, in [RFC 5322][rfc-5322-3-3] date and time format. The server SHOULD NOT make any assumptions about the accuracy of the client's clock. This header MAY be included in the request, but MUST be in this format when supplied. Greenwich Mean Time (GMT) MUST be used as the time zone reference for this header when it is provided. For example: `Wed, 24 Aug 2016 18:41:30 GMT`. Note that GMT is exactly equal to UTC (Coordinated Universal Time) for this purpose.
+Accept | Content type | The requested content type for the response such as:
application/xml
text/xml
application/json
text/javascript (for JSONP)
Per the HTTP guidelines, this is just a hint and responses MAY have a different content type, such as a blob fetch where a successful response will just be the blob stream as the payload. For services following OData, the preference order specified in OData SHOULD be followed.
+Accept-Encoding | Gzip, deflate | REST endpoints SHOULD support GZIP and DEFLATE encoding, when applicable. For very large resources, services MAY ignore and return uncompressed data.
+Accept-Language | "en", "es", etc. | Specifies the preferred language for the response. Services are not required to support this, but if a service supports localization it MUST do so through the Accept-Language header.
+Accept-Charset | Charset type like "UTF-8" | Default is UTF-8, but services SHOULD be able to handle ISO-8859-1.
+Content-Type | Content type | Mime type of request body (PUT/POST/PATCH)
+Prefer | return=minimal, return=representation | If the return=minimal preference is specified, services SHOULD return an empty body in response to a successful insert or update. If return=representation is specified, services SHOULD return the created or updated resource in the response. Services SHOULD support this header if they have scenarios where clients would sometimes benefit from responses, but sometimes the response would impose too much of a hit on bandwidth.
+If-Match, If-None-Match, If-Range | String | Services that support updates to resources using optimistic concurrency control MUST support the If-Match header to do so. Services MAY also use other headers related to ETags as long as they follow the HTTP specification.
+
+### 7.6. Standard response headers
+Services SHOULD return the following response headers, except where noted in the "required" column.
+
+Response Header | Required | Description
+------------------ | --------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+Date | All responses | Timestamp the response was processed, based on the server's clock, in [RFC 5322][rfc-5322-3-3] date and time format. This header MUST be included in the response. Greenwich Mean Time (GMT) MUST be used as the time zone reference for this header. For example: `Wed, 24 Aug 2016 18:41:30 GMT`. Note that GMT is exactly equal to UTC (Coordinated Universal Time) for this purpose.
+Content-Type | All responses | The content type
+Content-Encoding | All responses | GZIP or DEFLATE, as appropriate
+Preference-Applied | When specified in request | Whether a preference indicated in the Prefer request header was applied
+ETag | When the requested resource has an entity tag | The ETag response-header field provides the current value of the entity tag for the requested variant. Used with If-Match, If-None-Match and If-Range to implement optimistic concurrency control.
+
+### 7.7. Custom headers
+Custom headers MUST NOT be required for the basic operation of a given API.
+
+Some of the guidelines in this document prescribe the use of nonstandard HTTP headers.
+In addition, some services MAY need to add extra functionality, which is exposed via HTTP headers.
+The following guidelines help maintain consistency across usage of custom headers.
+
+Headers that are not standard HTTP headers MUST have one of two formats:
+
+1. A generic format for headers that are registered as "provisional" with IANA ([RFC 3864][rfc-3864])
+2. A scoped format for headers that are too usage-specific for registration
+
+These two formats are described below.
+
+### 7.8. Specifying headers as query parameters
+Some headers pose challenges for some scenarios such as AJAX clients, especially when making cross-domain calls where adding headers MAY not be supported.
+As such, some headers MAY be accepted as Query Parameters in addition to headers, with the same naming as the header:
+
+Not all headers make sense as query parameters, including most standard HTTP headers.
+
+The criteria for considering when to accept headers as parameters are:
+
+1. Any custom headers MUST be also accepted as parameters.
+2. Required standard headers MAY be accepted as parameters.
+3. Required headers with security sensitivity (e.g., Authorization header) MIGHT NOT be appropriate as parameters; the service owner SHOULD evaluate these on a case-by-case basis.
+
+The one exception to this rule is the Accept header.
+It's common practice to use a scheme with simple names instead of the full functionality described in the HTTP specification for Accept.
+
+### 7.9. PII parameters
+Consistent with their organization's privacy policy, clients SHOULD NOT transmit personally identifiable information (PII) parameters in the URL (as part of path or query string) because this information can be inadvertently exposed via client, network, and server logs and other mechanisms.
+
+Consequently, a service SHOULD accept PII parameters transmitted as headers.
+
+However, there are many scenarios where the above recommendations cannot be followed due to client or software limitations.
+To address these limitations, services SHOULD also accept these PII parameters as part of the URL consistent with the rest of these guidelines.
+
+Services that accept PII parameters -- whether in the URL or as headers -- SHOULD be compliant with privacy policy specified by their organization's engineering leadership.
+This will typically include recommending that clients prefer headers for transmission and implementations adhere to special precautions to ensure that logs and other service data collection are properly handled.
+
+### 7.10. Response formats
+For organizations to have a successful platform, they must serve data in formats developers are accustomed to using, and in consistent ways that allow developers to handle responses with common code.
+
+Web-based communication, especially when a mobile or other low-bandwidth client is involved, has moved quickly in the direction of JSON for a variety of reasons, including its tendency to be lighter weight and its ease of consumption with JavaScript-based clients.
+
+JSON property names SHOULD be camelCased.
+
+Services SHOULD provide JSON as the default encoding.
+
+#### 7.10.1. Clients-specified response format
+In HTTP, response format SHOULD be requested by the client using the Accept header.
+This is a hint, and the server MAY ignore it if it chooses to, even if this isn't typical of well-behaved servers.
+Clients MAY send multiple Accept headers and the service MAY choose one of them.
+
+The default response format (no Accept header provided) SHOULD be application/json, and all services MUST support application/json.
+
+Accept Header | Response type | Notes
+---------------- | ---------------------------------- | -------------------------------------------
+application/json | Payload SHOULD be returned as JSON | Also accept text/javascript for JSONP cases
+
+```http
+GET https://api.contoso.com/v1.0/products/user
+Accept: application/json
+```
+
+#### 7.10.2. Error condition responses
+For non-success conditions, developers SHOULD be able to write one piece of code that handles errors consistently across different Microsoft REST API Guidelines services.
+This allows building of simple and reliable infrastructure to handle exceptions as a separate flow from successful responses.
+The following is based on the OData v4 JSON spec.
+However, it is very generic and does not require specific OData constructs.
+APIs SHOULD use this format even if they are not using other OData constructs.
+
+The error response MUST be a single JSON object.
+This object MUST have a name/value pair named "error". The value MUST be a JSON object.
+
+This object MUST contain name/value pairs with the names "code" and "message", and it MAY contain name/value pairs with the names "target", "details" and "innererror."
+
+The value for the "code" name/value pair is a language-independent string.
+Its value is a service-defined error code that SHOULD be human-readable.
+This code serves as a more specific indicator of the error than the HTTP error code specified in the response.
+Services SHOULD have a relatively small number (about 20) of possible values for "code", and all clients MUST be capable of handling all of them.
+Most services will require a much larger number of more specific error codes, which are not interesting to all clients.
+These error codes SHOULD be exposed in the "innererror" name/value pair as described below.
+Introducing a new value for "code" that is visible to existing clients is a breaking change and requires a version increase.
+Services can avoid breaking changes by adding new error codes to "innererror" instead.
+
+The value for the "message" name/value pair MUST be a human-readable representation of the error.
+It is intended as an aid to developers and is not suitable for exposure to end users.
+Services wanting to expose a suitable message for end users MUST do so through an [annotation][odata-json-annotations] or custom property.
+Services SHOULD NOT localize "message" for the end user, because doing so might make the value unreadable to the app developer who may be logging the value, as well as make the value less searchable on the Internet.
+
+The value for the "target" name/value pair is the target of the particular error (e.g., the name of the property in error).
+
+The value for the "details" name/value pair MUST be an array of JSON objects that MUST contain name/value pairs for "code" and "message", and MAY contain a name/value pair for "target", as described above.
+The objects in the "details" array usually represent distinct, related errors that occurred during the request.
+See example below.
+
+The value for the "innererror" name/value pair MUST be an object.
+The contents of this object are service-defined.
+Services wanting to return more specific errors than the root-level code MUST do so by including a name/value pair for "code" and a nested "innererror". Each nested "innererror" object represents a higher level of detail than its parent.
+When evaluating errors, clients MUST traverse through all of the nested "innererrors" and choose the deepest one that they understand.
+This scheme allows services to introduce new error codes anywhere in the hierarchy without breaking backwards compatibility, so long as old error codes still appear.
+The service MAY return different levels of depth and detail to different callers.
+For example, in development environments, the deepest "innererror" MAY contain internal information that can help debug the service.
+To guard against potential security concerns around information disclosure, services SHOULD take care not to expose too much detail unintentionally.
+Error objects MAY also include custom server-defined name/value pairs that MAY be specific to the code.
+Error types with custom server-defined properties SHOULD be declared in the service's metadata document.
+See example below.
+
+Error responses MAY contain [annotations][odata-json-annotations] in any of their JSON objects.
+
+We recommend that for any transient errors that may be retried, services SHOULD include a Retry-After HTTP header indicating the minimum number of seconds that clients SHOULD wait before attempting the operation again.
+
+##### ErrorResponse : Object
+
+Property | Type | Required | Description
+-------- | ---- | -------- | -----------
+`error` | Error | ✔ | The error object.
+
+##### Error : Object
+
+Property | Type | Required | Description
+-------- | ---- | -------- | -----------
+`code` | String | ✔ | One of a server-defined set of error codes.
+`message` | String | ✔ | A human-readable representation of the error.
+`target` | String | | The target of the error.
+`details` | Error[] | | An array of details about specific errors that led to this reported error.
+`innererror` | InnerError | | An object containing more specific information than the current object about the error.
+
+##### InnerError : Object
+
+Property | Type | Required | Description
+-------- | ---- | -------- | -----------
+`code` | String | | A more specific error code than was provided by the containing error.
+`innererror` | InnerError | | An object containing more specific information than the current object about the error.
+
+##### Examples
+
+Example of "innererror":
+
+```json
+{
+ "error": {
+ "code": "BadArgument",
+ "message": "Previous passwords may not be reused",
+ "target": "password",
+ "innererror": {
+ "code": "PasswordError",
+ "innererror": {
+ "code": "PasswordDoesNotMeetPolicy",
+ "minLength": "6",
+ "maxLength": "64",
+ "characterTypes": ["lowerCase","upperCase","number","symbol"],
+ "minDistinctCharacterTypes": "2",
+ "innererror": {
+ "code": "PasswordReuseNotAllowed"
+ }
+ }
+ }
+ }
+}
+```
+
+In this example, the most basic error code is "BadArgument", but for clients that are interested, there are more specific error codes in "innererror."
+The "PasswordReuseNotAllowed" code may have been added by the service at a later date, having previously only returned "PasswordDoesNotMeetPolicy."
+Existing clients do not break when the new error code is added, but new clients MAY take advantage of it.
+The "PasswordDoesNotMeetPolicy" error also includes additional name/value pairs that allow the client to determine the server's configuration, validate the user's input programmatically, or present the server's constraints to the user within the client's own localized messaging.
+
+Example of "details":
+
+```json
+{
+ "error": {
+ "code": "BadArgument",
+ "message": "Multiple errors in ContactInfo data",
+ "target": "ContactInfo",
+ "details": [
+ {
+ "code": "NullValue",
+ "target": "PhoneNumber",
+ "message": "Phone number must not be null"
+ },
+ {
+ "code": "NullValue",
+ "target": "LastName",
+ "message": "Last name must not be null"
+ },
+ {
+ "code": "MalformedValue",
+ "target": "Address",
+ "message": "Address is not valid"
+ }
+ ]
+ }
+}
+```
+
+In this example there were multiple problems with the request, with each individual error listed in "details."
+
+### 7.11. HTTP Status Codes
+Standard HTTP Status Codes SHOULD be used; see the HTTP Status Code definitions for more information.
+
+### 7.12. Client library optional
+Developers MUST be able to develop on a wide variety of platforms and languages, such as Windows, macOS, Linux, C#, Python, Node.js, and Ruby.
+
+Services SHOULD be able to be accessed from simple HTTP tools such as curl without significant effort.
+
+Service developer portals SHOULD provide the equivalent of "Get Developer Token" to facilitate experimentation and curl support.
+
+## 8. CORS
+Services compliant with the Microsoft REST API Guidelines MUST support [CORS (Cross Origin Resource Sharing)][cors].
+Services SHOULD support an allowed origin of CORS * and enforce authorization through valid OAuth tokens.
+Services SHOULD NOT support user credentials with origin validation.
+There MAY be exceptions for special cases.
+
+### 8.1. Client guidance
+Web developers usually don't need to do anything special to take advantage of CORS.
+All of the handshake steps happen invisibly as part of the standard XMLHttpRequest calls they make.
+
+Many other platforms, such as .NET, have integrated support for CORS.
+
+#### 8.1.1. Avoiding preflight
+Because the CORS protocol can trigger preflight requests that add additional round trips to the server, performance-critical apps might be interested in avoiding them.
+The spirit behind CORS is to avoid preflight for any simple cross-domain requests that old non-CORS-capable browsers were able to make.
+All other requests require preflight.
+
+A request is "simple" and avoids preflight if its method is GET, HEAD or POST, and if it doesn't contain any request headers besides Accept, Accept-Language and Content-Language.
+For POST requests, the Content-Type header is also allowed, but only if its value is "application/x-www-form-urlencoded", "multipart/form-data" or "text/plain."
+For any other headers or values, a preflight request will happen.
+
+### 8.2. Service guidance
+ At minimum, services MUST:
+- Understand the Origin request header that browsers send on cross-domain requests, and the Access-Control-Request-Method request header that they send on preflight OPTIONS requests that check for access.
+- If the Origin header is present in a request:
+ - If the request uses the OPTIONS method and contains the Access-Control-Request-Method header, then it is a preflight request intended to probe for access before the actual request. Otherwise, it is an actual request. For preflight requests, beyond performing the steps below to add headers, services MUST perform no additional processing and MUST return a 200 OK. For non-preflight requests, the headers below are added in addition to the request's regular processing.
+ - Add an Access-Control-Allow-Origin header to the response, containing the same value as the Origin request header. Note that this requires services to dynamically generate the header value. Resources that do not require cookies or any other form of [user credentials][cors-user-credentials] MAY respond with a wildcard asterisk (*) instead. Note that the wildcard is acceptable here only, and not for any of the other headers described below.
+ - If the caller requires access to a response header that is not in the set of [simple response headers][cors-simple-headers] (Cache-Control, Content-Language, Content-Type, Expires, Last-Modified, Pragma), then add an Access-Control-Expose-Headers header containing the list of additional response header names the client should have access to.
+ - If the request requires cookies, then add an Access-Control-Allow-Credentials header set to "true."
+ - If the request was a preflight request (see first bullet), then the service MUST:
+ - Add an Access-Control-Allow-Headers response header containing the list of request header names the client is permitted to use. This list need only contain headers that are not in the set of [simple request headers][cors-simple-headers] (Accept, Accept-Language, Content-Language). If there are no restrictions on headers the service accepts, the service MAY simply return the same value as the Access-Control-Request-Headers header sent by the client.
+ - Add an Access-Control-Allow-Methods response header containing the list of HTTP methods the caller is permitted to use.
+
+Add an Access-Control-Max-Age pref response header containing the number of seconds for which this preflight response is valid (and hence can be avoided before subsequent actual requests). Note that while it is customary to use a large value like 2592000 (30 days), many browsers self-impose a much lower limit (e.g., five minutes).
+
+Because browser preflight response caches are notoriously weak, the additional round trip from a preflight response hurts performance.
+Services used by interactive Web clients where performance is critical SHOULD avoid patterns that cause a preflight request
+- For GET and HEAD calls, avoid requiring request headers that are not part of the simple set above. Allow them to be provided as query parameters instead.
+ - The Authorization header is not part of the simple set, so the authentication token MUST be sent through the "access_token" query parameter instead, for resources requiring authentication. Note that passing authentication tokens in the URL is not recommended, because it can lead to the token getting recorded in server logs and exposed to anyone with access to those logs. Services that accept authentication tokens through the URL MUST take steps to mitigate the security risks, such as using short-lived authentication tokens, suppressing the auth token from getting logged, and controlling access to server logs.
+
+- Avoid requiring cookies. XmlHttpRequest will only send cookies on cross-domain requests if the "withCredentials" attribute is set; this also causes a preflight request.
+ - Services that require cookie-based authentication MUST use a "dynamic canary" to secure all APIs that accept cookies.
+
+- For POST calls, prefer simple Content-Types in the set of ("application/x-www-form-urlencoded", "multipart/form-data", "text/plain") where applicable. Any other Content-Type will induce a preflight request.
+ - Services MUST NOT contravene other API recommendations in the name of avoiding CORS preflight requests. In particular, in accordance with recommendations, most POST requests will actually require a preflight request due to the Content-Type.
+ - If eliminating preflight is critical, then a service MAY support alternative mechanisms for data transfer, but the RECOMMENDED approach MUST also be supported.
+
+In addition, when appropriate services MAY support the JSONP pattern for simple, GET-only cross-domain access.
+In JSONP, services take a parameter indicating the format (_$format=json_) and a parameter indicating a callback (_$callback=someFunc_), and return a text/javascript document containing the JSON response wrapped in a function call with the indicated name.
+More on JSONP at Wikipedia: [JSONP](https://en.wikipedia.org/wiki/JSONP).
+
+## 9. Collections
+### 9.1. Item keys
+Services MAY support durable identifiers for each item in the collection, and that identifier SHOULD be represented in JSON as "id". These durable identifiers are often used as item keys.
+
+Collections that support durable identifiers MAY support delta queries.
+
+### 9.2. Serialization
+Collections are represented in JSON using standard array notation.
+
+### 9.3. Collection URL patterns
+Collections are located directly under the service root when they are top level, or as a segment under another resource when scoped to that resource.
+
+For example:
+
+```http
+GET https://api.contoso.com/v1.0/people
+```
+
+Whenever possible, services MUST support the "/" pattern.
+For example:
+
+```http
+GET https://{serviceRoot}/{collection}/{id}
+```
+
+Where:
+- {serviceRoot} – the combination of host (site URL) + the root path to the service
+- {collection} – the name of the collection, unabbreviated, pluralized
+- {id} – the value of the unique id property. When using the "/" pattern this MUST be the raw string/number/guid value with no quoting but properly escaped to fit in a URL segment.
+
+#### 9.3.1. Nested collections and properties
+Collection items MAY contain other collections.
+For example, a user collection MAY contain user resources that have multiple addresses:
+
+```http
+GET https://api.contoso.com/v1.0/people/123/addresses
+```
+
+```json
+{
+ "value": [
+ { "street": "1st Avenue", "city": "Seattle" },
+ { "street": "124th Ave NE", "city": "Redmond" }
+ ]
+}
+```
+
+### 9.4. Big collections
+As data grows, so do collections.
+Planning for pagination is important for all services.
+Therefore, when multiple pages are available, the serialization payload MUST contain the opaque URL for the next page as appropriate.
+Refer to the paging guidance for more details.
+
+Clients MUST be resilient to collection data being either paged or nonpaged for any given request.
+
+```json
+{
+ "value":[
+ { "id": "Item 1","price": 99.95,"sizes": null},
+ { … },
+ { … },
+ { "id": "Item 99","price": 59.99,"sizes": null}
+ ],
+ "@nextLink": "{opaqueUrl}"
+}
+```
+
+### 9.5. Changing collections
+POST requests are not idempotent.
+This means that two POST requests sent to a collection resource with exactly the same payload MAY lead to multiple items being created in that collection.
+This is often the case for insert operations on items with a server-side generated id.
+
+For example, the following request:
+
+```http
+POST https://api.contoso.com/v1.0/people
+```
+
+Would lead to a response indicating the location of the new collection item:
+
+```http
+201 Created
+Location: https://api.contoso.com/v1.0/people/123
+```
+
+And once executed again, would likely lead to another resource:
+
+```http
+201 Created
+Location: https://api.contoso.com/v1.0/people/124
+```
+
+While a PUT request would require the indication of the collection item with the corresponding key instead:
+
+```http
+PUT https://api.contoso.com/v1.0/people/123
+```
+
+### 9.6. Sorting collections
+The results of a collection query MAY be sorted based on property values.
+The property is determined by the value of the _$orderBy_ query parameter.
+
+The value of the _$orderBy_ parameter contains a comma-separated list of expressions used to sort the items.
+A special case of such an expression is a property path terminating on a primitive property.
+
+The expression MAY include the suffix "asc" for ascending or "desc" for descending, separated from the property name by one or more spaces.
+If "asc" or "desc" is not specified, the service MUST order by the specified property in ascending order.
+
+NULL values MUST sort as "less than" non-NULL values.
+
+Items MUST be sorted by the result values of the first expression, and then items with the same value for the first expression are sorted by the result value of the second expression, and so on.
+The sort order is the inherent order for the type of the property.
+
+For example:
+
+```http
+GET https://api.contoso.com/v1.0/people?$orderBy=name
+```
+
+Will return all people sorted by name in ascending order.
+
+For example:
+
+```http
+GET https://api.contoso.com/v1.0/people?$orderBy=name desc
+```
+
+Will return all people sorted by name in descending order.
+
+Sub-sorts can be specified by a comma-separated list of property names with OPTIONAL direction qualifier.
+
+For example:
+
+```http
+GET https://api.contoso.com/v1.0/people?$orderBy=name desc,hireDate
+```
+
+Will return all people sorted by name in descending order and a secondary sort order of hireDate in ascending order.
+
+Sorting MUST compose with filtering such that:
+
+```http
+GET https://api.contoso.com/v1.0/people?$filter=name eq 'david'&$orderBy=hireDate
+```
+
+Will return all people whose name is David sorted in ascending order by hireDate.
+
+#### 9.6.1. Interpreting a sorting expression
+Sorting parameters MUST be consistent across pages, as both client and server-side paging is fully compatible with sorting.
+
+If a service does not support sorting by a property named in a _$orderBy_ expression, the service MUST respond with an error message as defined in the Responding to Unsupported Requests section.
+
+### 9.7. Filtering
+The _$filter_ querystring parameter allows clients to filter a collection of resources that are addressed by a request URL.
+The expression specified with _$filter_ is evaluated for each resource in the collection, and only items where the expression evaluates to true are included in the response.
+Resources for which the expression evaluates to false or to null, or which reference properties that are unavailable due to permissions, are omitted from the response.
+
+Example: return all Products whose Price is less than $10.00
+
+```http
+GET https://api.contoso.com/v1.0/products?$filter=price lt 10.00
+```
+
+The value of the _$filter_ option is a Boolean expression.
+
+#### 9.7.1. Filter operations
+Services that support _$filter_ SHOULD support the following minimal set of operations.
+
+Operator | Description | Example
+-------------------- | --------------------- | -----------------------------------------------------
+Comparison Operators | |
+eq | Equal | city eq 'Redmond'
+ne | Not equal | city ne 'London'
+gt | Greater than | price gt 20
+ge | Greater than or equal | price ge 10
+lt | Less than | price lt 20
+le | Less than or equal | price le 100
+Logical Operators | |
+and | Logical and | price le 200 and price gt 3.5
+or | Logical or | price le 3.5 or price gt 200
+not | Logical negation | not price le 3.5
+Grouping Operators | |
+( ) | Precedence grouping | (priority eq 1 or city eq 'Redmond') and price gt 100
+
+#### 9.7.2. Operator examples
+The following examples illustrate the use and semantics of each of the logical operators.
+
+Example: all products with a name equal to 'Milk'
+
+```http
+GET https://api.contoso.com/v1.0/products?$filter=name eq 'Milk'
+```
+
+Example: all products with a name not equal to 'Milk'
+
+```http
+GET https://api.contoso.com/v1.0/products?$filter=name ne 'Milk'
+```
+
+Example: all products with the name 'Milk' that also have a price less than 2.55:
+
+```http
+GET https://api.contoso.com/v1.0/products?$filter=name eq 'Milk' and price lt 2.55
+```
+
+Example: all products that either have the name 'Milk' or have a price less than 2.55:
+
+```http
+GET https://api.contoso.com/v1.0/products?$filter=name eq 'Milk' or price lt 2.55
+```
+
+Example: all products that have the name 'Milk' or 'Eggs' and have a price less than 2.55:
+
+```http
+GET https://api.contoso.com/v1.0/products?$filter=(name eq 'Milk' or name eq 'Eggs') and price lt 2.55
+```
+
+#### 9.7.3. Operator precedence
+Services MUST use the following operator precedence for supported operators when evaluating _$filter_ expressions.
+Operators are listed by category in order of precedence from highest to lowest.
+Operators in the same category have equal precedence:
+
+| Group | Operator | Description |
+|:----------------|:---------|:----------------------|
+| Grouping | ( ) | Precedence grouping |
+| Unary | not | Logical Negation |
+| Relational | gt | Greater Than |
+| | ge | Greater than or Equal |
+| | lt | Less Than |
+| | le | Less than or Equal |
+| Equality | eq | Equal |
+| | ne | Not Equal |
+| Conditional AND | and | Logical And |
+| Conditional OR | or | Logical Or |
+
+### 9.8. Pagination
+RESTful APIs that return collections MAY return partial sets.
+Consumers of these services MUST expect partial result sets and correctly page through to retrieve an entire set.
+
+There are two forms of pagination that MAY be supported by RESTful APIs.
+Server-driven paging mitigates against denial-of-service attacks by forcibly paginating a request over multiple response payloads.
+Client-driven paging enables clients to request only the number of resources that it can use at a given time.
+
+Sorting and Filtering parameters MUST be consistent across pages, because both client- and server-side paging is fully compatible with both filtering and sorting.
+
+#### 9.8.1. Server-driven paging
+Paginated responses MUST indicate a partial result by including a continuation token in the response.
+The absence of a continuation token means that no additional pages are available.
+
+Clients MUST treat the continuation URL as opaque, which means that query options may not be changed while iterating over a set of partial results.
+
+Example:
+
+```http
+GET http://api.contoso.com/v1.0/people HTTP/1.1
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ ...,
+ "value": [...],
+ "@nextLink": "{opaqueUrl}"
+}
+```
+
+#### 9.8.2. Client-driven paging
+Clients MAY use _$top_ and _$skip_ query parameters to specify a number of results to return and an offset into the collection.
+
+The server SHOULD honor the values specified by the client; however, clients MUST be prepared to handle responses that contain a different page size or contain a continuation token.
+
+When both _$top_ and _$skip_ are given by a client, the server SHOULD first apply _$skip_ and then _$top_ on the collection.
+
+Note: If the server can't honor _$top_ and/or _$skip_, the server MUST return an error to the client informing about it instead of just ignoring the query options.
+This will avoid the risk of the client making assumptions about the data returned.
+
+Example:
+
+```http
+GET http://api.contoso.com/v1.0/people?$top=5&$skip=2 HTTP/1.1
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ ...,
+ "value": [...]
+}
+```
+
+#### 9.8.3. Additional considerations
+**Stable order prerequisite:** Both forms of paging depend on the collection of items having a stable order.
+The server MUST supplement any specified order criteria with additional sorts (typically by key) to ensure that items are always ordered consistently.
+
+**Missing/repeated results:** Even if the server enforces a consistent sort order, results MAY be missing or repeated based on creation or deletion of other resources.
+Clients MUST be prepared to deal with these discrepancies.
+The server SHOULD always encode the record ID of the last read record, helping the client in the process of managing repeated/missing results.
+
+**Combining client- and server-driven paging:** Note that client-driven paging does not preclude server-driven paging.
+If the page size requested by the client is larger than the default page size supported by the server, the expected response would be the number of results specified by the client, paginated as specified by the server paging settings.
+
+**Page Size:** Clients MAY request server-driven paging with a specific page size by specifying a _$maxpagesize_ preference.
+The server SHOULD honor this preference if the specified page size is smaller than the server's default page size.
+
+**Paginating embedded collections:** It is possible for both client-driven paging and server-driven paging to be applied to embedded collections.
+If a server paginates an embedded collection, it MUST include additional continuation tokens as appropriate.
+
+**Recordset count:** Developers who want to know the full number of records across all pages, MAY include the query parameter _$count=true_ to tell the server to include the count of items in the response.
+
+### 9.9. Compound collection operations
+Filtering, Sorting and Pagination operations MAY all be performed against a given collection.
+When these operations are performed together, the evaluation order MUST be:
+
+1. **Filtering**. This includes all range expressions performed as an AND operation.
+2. **Sorting**. The potentially filtered list is sorted according to the sort criteria.
+3. **Pagination**. The materialized paginated view is presented over the filtered, sorted list. This applies to both server-driven pagination and client-driven pagination.
+
+### 9.10. Empty Results
+When a filter is performed on a collection and the result set is empty you MUST respond with a valid response body and a 200 response code.
+In this example the filters supplied by the client resulted in a empty result set.
+The response body is returned as normal and the _value_ attribute is set to a empty collection.
+A client MAY be expecting metadata attributes like _maxItems_ based on the format of your responses to similar calls which produced results.
+You SHOULD maintain consistency in your API whenever possible.
+
+```http
+GET https://api.contoso.com/v1.0/products?$filter=(name eq 'Milk' or name eq 'Eggs') and price lt 2.55
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ ...,
+ "maxItems": 0,
+ "value": []
+}
+```
+
+## 10. Delta queries
+Services MAY choose to support delta queries.
+
+### 10.1. Delta links
+Delta links are opaque, service-generated links that the client uses to retrieve subsequent changes to a result.
+
+At a conceptual level delta links are based on a defining query that describes the set of results for which changes are being tracked.
+The delta link encodes the collection of entities for which changes are being tracked, along with a starting point from which to track changes.
+
+If the query contains a filter, the response MUST include only changes to entities matching the specified criteria.
+The key principles of the Delta Query are:
+- Every item in the set MUST have a persistent identifier. That identifier SHOULD be represented as "id". This identifier is a service defined opaque string that MAY be used by the client to track object across calls.
+- The delta MUST contain an entry for each entity that newly matches the specified criteria, and MUST contain a "@removed" entry for each entity that no longer matches the criteria.
+- Re-evaluate the query and compare it to original set of results; every entry uniquely in the current set MUST be returned as an Add operation, and every entry uniquely in the original set MUST be returned as a "remove" operation.
+- Each entity that previously did not match the criteria but matches it now MUST be returned as an "add"; conversely, each entity that previously matched the query but no longer does MUST be returned as a "@removed" entry.
+- Entities that have changed MUST be included in the set using their standard representation.
+- Services MAY add additional metadata to the "@removed" node, such as a reason for removal, or a "removed at" timestamp. We recommend teams coordinate with the Microsoft REST API Guidelines Working Group on extensions to help maintain consistency.
+
+The delta link MUST NOT encode any client top or skip value.
+
+### 10.2. Entity representation
+Added and updated entities are represented in the entity set using their standard representation.
+From the perspective of the set, there is no difference between an added or updated entity.
+
+Removed entities are represented using only their "id" and an "@removed" node.
+The presence of an "@removed" node MUST represent the removal of the entry from the set.
+
+### 10.3. Obtaining a delta link
+A delta link is obtained by querying a collection or entity and appending a $delta query string parameter.
+For example:
+
+```http
+GET https://api.contoso.com/v1.0/people?$delta
+HTTP/1.1
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ "value":[
+ { "id": "1", "name": "Matt"},
+ { "id": "2", "name": "Mark"},
+ { "id": "3", "name": "John"}
+ ],
+ "@deltaLink": "{opaqueUrl}"
+}
+```
+
+Note: If the collection is paginated the deltaLink will only be present on the final page but MUST reflect any changes to the data returned across all pages.
+
+### 10.4. Contents of a delta link response
+Added/Updated entries MUST appear as regular JSON objects, with regular item properties.
+Returning the added/modified items in their regular representation allows the client to merge them into their existing "cache" using standard merge concepts based on the "id" field.
+
+Entries removed from the defined collection MUST be included in the response.
+Items removed from the set MUST be represented using only their "id" and an "@removed" node.
+
+### 10.5. Using a delta link
+The client requests changes by invoking the GET method on the delta link.
+The client MUST use the delta URL as is -- in other words the client MUST NOT modify the URL in any way (e.g., parsing it and adding additional query string parameters).
+In this example:
+
+```http
+GET https://{opaqueUrl} HTTP/1.1
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ "value":[
+ { "id": "1", "name": "Mat"},
+ { "id": "2", "name": "Marc"},
+ { "id": "3", "@removed": {} },
+ { "id": "4", "name": "Luc"}
+ ],
+ "@deltaLink": "{opaqueUrl}"
+}
+```
+
+The results of a request against the delta link may span multiple pages but MUST be ordered by the service across all pages in such a way as to ensure a deterministic result when applied in order to the response that contained the delta link.
+
+If no changes have occurred, the response is an empty collection that contains a delta link for subsequent changes if requested.
+This delta link MAY be identical to the delta link resulting in the empty collection of changes.
+
+If the delta link is no longer valid, the service MUST respond with _410 Gone_. The response SHOULD include a Location header that the client can use to retrieve a new baseline set of results.
+
+## 11. JSON standardizations
+### 11.1. JSON formatting standardization for primitive types
+Primitive values MUST be serialized to JSON following the rules of [RFC8259][rfc-8259].
+
+**Important note for 64bit integers:** JavaScript will silently truncate integers larger than `Number.MAX_SAFE_INTEGER` (2^53-1) or numbers smaller than `Number.MIN_SAFE_INTEGER` (-2^53+1). If the service is expected to return integer values outside the range of safe values, strongly consider returning the value as a string in order to maximize interoperability and avoid data loss.
+
+### 11.2. Guidelines for dates and times
+#### 11.2.1. Producing dates
+Services MUST produce dates using the `DateLiteral` format, and SHOULD use the `Iso8601Literal` format unless there are compelling reasons to do otherwise.
+Services that do use the `StructuredDateLiteral` format MUST NOT produce dates using the `T` kind unless BOTH the additional precision is REQUIRED, and ECMAScript clients are explicitly unsupported.
+(Non-Normative statement: When deciding which particular `DateKind` to standardize on, the approximate order of preference is `E, C, U, W, O, X, I, T`.
+This optimizes for ECMAScript, .NET, and C++ programmers, in that order.)
+
+#### 11.2.2. Consuming dates
+Services MUST accept dates from clients that use the same `DateLiteral` format (including the `DateKind`, if applicable) that they produce, and SHOULD accept dates using any `DateLiteral` format.
+
+#### 11.2.3. Compatibility
+Services MUST use the same `DateLiteral` format (including the same `DateKind`, if applicable) for all resources of the same type, and SHOULD use the same `DateLiteral` format (and `DateKind`, if applicable) for all resources across the entire service.
+
+Any change to the `DateLiteral` format produced by the service (including the `DateKind`, if applicable) and any reductions in the `DateLiteral` formats (and `DateKind`, if applicable) accepted by the service MUST be treated as a breaking change.
+Any widening of the `DateLiteral` formats accepted by the service is NOT considered a breaking change.
+
+### 11.3. JSON serialization of dates and times
+Round-tripping serialized dates with JSON is a hard problem.
+Although ECMAScript supports literals for most built-in types, it does not define a literal format for dates.
+The Web has coalesced around the [ECMAScript subset of ISO 8601 date formats (ISO 8601)][iso-8601], but there are situations where this format is not desirable.
+For those cases, this document defines a JSON serialization format that can be used to unambiguously represent dates in different formats.
+Other serialization formats (such as XML) could be derived from this format.
+
+#### 11.3.1. The `DateLiteral` format
+Dates represented in JSON are serialized using the following grammar.
+Informally, a `DateValue` is either an ISO 8601-formatted string or a JSON object containing two properties named `kind` and `value` that together define a point in time.
+The following is not a context-free grammar; in particular, the interpretation of `DateValue` depends on the value of `DateKind`, but this minimizes the number of productions required to describe the format.
+
+```
+DateLiteral:
+ Iso8601Literal
+ StructuredDateLiteral
+
+Iso8601Literal:
+ A string literal as defined in https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15. Note that the full grammar for ISO 8601 (such as "basic format" without separators) is not supported.
+ All dates default to UTC unless specified otherwise.
+
+StructuredDateLiteral:
+ { DateKindProperty , DateValueProperty }
+ { DateValueProperty , DateKindProperty }
+
+DateKindProperty
+ "kind" : DateKind
+
+DateKind:
+ "C" ; see below
+ "E" ; see below
+ "I" ; see below
+ "O" ; see below
+ "T" ; see below
+ "U" ; see below
+ "W" ; see below
+ "X" ; see below
+
+DateValueProperty:
+ "value" : DateValue
+
+DateValue:
+ UnsignedInteger ; not defined here
+ SignedInteger ; not defined here
+ RealNumber ; not defined here
+ Iso8601Literal ; as above
+```
+
+#### 11.3.2. Commentary on date formatting
+A `DateLiteral` using the `Iso8601Literal` production is relatively straightforward.
+Here is an example of an object with a property named `creationDate` that is set to February 13, 2015, at 1:15 p.m. UTC:
+
+```json
+{ "creationDate" : "2015-02-13T13:15Z" }
+```
+
+The `StructuredDateLiteral` consists of a `DateKind` and an accompanying `DateValue` whose valid values (and their interpretation) depend on the `DateKind`. The following table describes the valid combinations and their meaning:
+
+DateKind | DateValue | Colloquial Name & Interpretation | More Info
+-------- | --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------
+C | UnsignedInteger | "CLR"; number of milliseconds since midnight January 1, 0001; negative values are not allowed. *See note below.* | [MSDN][clr-time]
+E | SignedInteger | "ECMAScript"; number of milliseconds since midnight, January 1, 1970. | [ECMA International][ecmascript-time]
+I | Iso8601Literal | "ISO 8601"; a string limited to the ECMAScript subset. |
+O | RealNumber | "OLE Date"; integral part is the number of days since midnight, December 31, 1899, and fractional part is the time within the day (0.5 = midday). | [MSDN][ole-date]
+T | SignedInteger | "Ticks"; number of ticks (100-nanosecond intervals) since midnight January 1, 1601. *See note below.* | [MSDN][ticks-time]
+U | SignedInteger | "UNIX"; number of seconds since midnight, January 1, 1970. | [MSDN][unix-time]
+W | SignedInteger | "Windows"; number of milliseconds since midnight January 1, 1601. *See note below.* | [MSDN][windows-time]
+X | RealNumber | "Excel"; as for `O` but the year 1900 is incorrectly treated as a leap year, and day 0 is "January 0 (zero)". | [Microsoft Support][excel-time]
+
+**Important note for `C` and `W` kinds:** The native CLR and Windows times are represented by 100-nanosecond "tick" values.
+To interoperate with ECMAScript clients that have limited precision, _these values MUST be converted to and from milliseconds_ when (de)serialized as a `DateLiteral`.
+One millisecond is equivalent to 10,000 ticks.
+
+**Important note for `T` kind:** This kind preserves the full fidelity of the Windows native time formats (and is trivially convertible to and from the native CLR format) but is incompatible with ECMAScript clients.
+Therefore, its use SHOULD be limited to only those scenarios that both require the additional precision and do not need to interoperate with ECMAScript clients.
+
+Here is the same example of an object with a property named creationDate that is set to February 13, 2015, at 1:15 p.m. UTC, using several formats:
+
+```json
+[
+ { "creationDate" : { "kind" : "O", "value" : 42048.55 } },
+ { "creationDate" : { "kind" : "E", "value" : 1423862100000 } }
+]
+```
+
+One of the benefits of separating the kind from the value is that once a client knows the kind used by a particular service, it can interpret the value without requiring any additional parsing.
+In the common case of the value being a number, this makes coding easier for developers:
+
+```csharp
+// We know this service always gives out ECMAScript-format dates
+var date = new Date(serverResponse.someObject.creationDate.value);
+```
+
+### 11.4. Durations
+[Durations][wikipedia-iso8601-durations] need to be serialized in conformance with [ISO 8601][wikipedia-iso8601-durations].
+Durations are "represented by the format `P[n]Y[n]M[n]DT[n]H[n]M[n]S`."
+From the standard:
+- P is the duration designator (historically called "period") placed at the start of the duration representation.
+- Y is the year designator that follows the value for the number of years.
+- M is the month designator that follows the value for the number of months.
+- W is the week designator that follows the value for the number of weeks.
+- D is the day designator that follows the value for the number of days.
+- T is the time designator that precedes the time components of the representation.
+- H is the hour designator that follows the value for the number of hours.
+- M is the minute designator that follows the value for the number of minutes.
+- S is the second designator that follows the value for the number of seconds.
+
+For example, "P3Y6M4DT12H30M5S" represents a duration of "three years, six months, four days, twelve hours, thirty minutes, and five seconds."
+
+### 11.5. Intervals
+[Intervals][wikipedia-iso8601-intervals] are defined as part of [ISO 8601][wikipedia-iso8601-intervals].
+- Start and end, such as "2007-03-01T13:00:00Z/2008-05-11T15:30:00Z"
+- Start and duration, such as "2007-03-01T13:00:00Z/P1Y2M10DT2H30M"
+- Duration and end, such as "P1Y2M10DT2H30M/2008-05-11T15:30:00Z"
+- Duration only, such as "P1Y2M10DT2H30M", with additional context information
+
+### 11.6. Repeating intervals
+[Repeating Intervals][wikipedia-iso8601-repeatingintervals], as per [ISO 8601][wikipedia-iso8601-repeatingintervals], are:
+
+> Formed by adding "R[n]/" to the beginning of an interval expression, where R is used as the letter itself and [n] is replaced by the number of repetitions.
+Leaving out the value for [n] means an unbounded number of repetitions.
+
+For example, to repeat the interval of "P1Y2M10DT2H30M" five times starting at "2008-03-01T13:00:00Z", use "R5/2008-03-01T13:00:00Z/P1Y2M10DT2H30M."
+
+## 12. Versioning
+**All APIs compliant with the Microsoft REST API Guidelines MUST support explicit versioning.** It's critical that clients can count on services to be stable over time, and it's critical that services can add features and make changes.
+
+### 12.1. Versioning formats
+Services are versioned using a Major.Minor versioning scheme.
+Services MAY opt for a "Major" only version scheme in which case the ".0" is implied and all other rules in this section apply.
+Two options for specifying the version of a REST API request are supported:
+- Embedded in the path of the request URL, at the end of the service root: `https://api.contoso.com/v1.0/products/users`
+- As a query string parameter of the URL: `https://api.contoso.com/products/users?api-version=1.0`
+
+Guidance for choosing between the two options is as follows:
+
+1. Services co-located behind a DNS endpoint MUST use the same versioning mechanism.
+2. In this scenario, a consistent user experience across the endpoint is paramount. The Microsoft REST API Guidelines Working Group recommends that new top-level DNS endpoints are not created without explicit conversations with your organization's leadership team.
+3. Services that guarantee the stability of their REST API's URL paths, even through future versions of the API, MAY adopt the query string parameter mechanism. This means the naming and structure of the relationships described in the API cannot evolve after the API ships, even across versions with breaking changes.
+4. Services that cannot ensure URL path stability across future versions MUST embed the version in the URL path.
+
+Certain bedrock services such as Microsoft's Azure Active Directory may be exposed behind multiple endpoints.
+Such services MUST support the versioning mechanisms of each endpoint, even if that means supporting multiple versioning mechanisms.
+
+#### 12.1.1. Group versioning
+Group versioning is an OPTIONAL feature that MAY be offered on services using the query string parameter mechanism.
+Group versions allow for logical grouping of API endpoints under a common versioning moniker.
+This allows developers to look up a single version number and use it across multiple endpoints.
+Group version numbers are well known, and services SHOULD reject any unrecognized values.
+
+Internally, services will take a Group Version and map it to the appropriate Major.Minor version.
+
+The Group Version format is defined as YYYY-MM-DD, for example 2012-12-07 for December 7, 2012. This Date versioning format applies only to Group Versions and SHOULD NOT be used as an alternative to Major.Minor versioning.
+
+##### Examples of group versioning
+
+| Group | Major.Minor |
+|:-----------|:------------|
+| 2012-12-01 | 1.0 |
+| | 1.1 |
+| | 1.2 |
+| 2013-03-21 | 1.0 |
+| | 2.0 |
+| | 3.0 |
+| | 3.1 |
+| | 3.2 |
+| | 3.3 |
+
+Version Format | Example | Interpretation
+----------------------------- | ---------------------- | ------------------------------------------
+{groupVersion} | 2013-03-21, 2012-12-01 | 3.3, 1.2
+{majorVersion} | 3 | 3.0
+{majorVersion}.{minorVersion} | 1.2 | 1.2
+
+Clients can specify either the group version or the Major.Minor version:
+
+For example:
+
+```http
+GET http://api.contoso.com/acct1/c1/blob2?api-version=1.0
+```
+
+```http
+PUT http://api.contoso.com/acct1/c1/b2?api-version=2011-12-07
+```
+
+### 12.2. When to version
+Services MUST increment their version number in response to any breaking API change.
+See the following section for a detailed discussion of what constitutes a breaking change.
+Services MAY increment their version number for nonbreaking changes as well, if desired.
+
+Use a new major version number to signal that support for existing clients will be deprecated in the future.
+When introducing a new major version, services MUST provide a clear upgrade path for existing clients and develop a plan for deprecation that is consistent with their business group's policies.
+Services SHOULD use a new minor version number for all other changes.
+
+Online documentation of versioned services MUST indicate the current support status of each previous API version and provide a path to the latest version.
+
+### 12.3. Definition of a breaking change
+Changes to the contract of an API are considered a breaking change.
+Changes that impact the backwards compatibility of an API are a breaking change.
+
+Teams MAY define backwards compatibility as their business needs require.
+For example, Azure defines the addition of a new JSON field in a response to be not backwards compatible.
+Office 365 has a looser definition of backwards compatibility and allows JSON fields to be added to responses.
+
+Clear examples of breaking changes:
+
+1. Removing or renaming APIs or API parameters
+2. Changes in behavior for an existing API
+3. Changes in Error Codes and Fault Contracts
+4. Anything that would violate the [Principle of Least Astonishment][principle-of-least-astonishment]
+
+Services MUST explicitly define their definition of a breaking change, especially with regard to adding new fields to JSON responses and adding new API arguments with default fields.
+Services that are co-located behind a DNS Endpoint with other services MUST be consistent in defining contract extensibility.
+
+The applicable changes described [in this section of the OData V4 spec][odata-breaking-changes] SHOULD be considered part of the minimum bar that all services MUST consider a breaking change.
+
+## 13. Long running operations
+Long running operations, sometimes called async operations, tend to mean different things to different people.
+This section sets forth guidance around different types of long running operations, and describes the wire protocols and best practices for these types of operations.
+
+1. One or more clients MUST be able to monitor and operate on the same resource at the same time.
+2. The state of the system SHOULD be discoverable and testable at all times. Clients SHOULD be able to determine the system state even if the operation tracking resource is no longer active. The act of querying the state of a long running operation should itself leverage principles of the web. i.e. well-defined resources with uniform interface semantics. Clients MAY issue a GET on some resource to determine the state of a long running operation
+3. Long running operations SHOULD work for clients looking to "Fire and Forget" and for clients looking to actively monitor and act upon results.
+4. Cancellation does not explicitly mean rollback. On a per-API defined case it may mean rollback, or compensation, or completion, or partial completion, etc. Following a cancelled operation, It SHOULD NOT be a client's responsibility to return the service to a consistent state which allows continued service.
+
+### 13.1. Resource based long running operations (RELO)
+Resource based modeling is where the status of an operation is encoded in the resource and the wire protocol used is the standard synchronous protocol.
+In this model state transitions are well defined and goal states are similarly defined.
+
+_This is the preferred model for long running operations and should be used wherever possible._ Avoiding the complexity and mechanics of the LRO Wire Protocol makes things simpler for our users and tooling chain.
+
+An example may be a machine reboot, where the operation itself completes synchronously but the GET operation on the virtual machine resource would have a "state: Rebooting", "state: Running" that could be queried at any time.
+
+This model MAY integrate Push Notifications.
+
+While most operations are likely to be POST semantics, in addition to POST semantics, services MAY support PUT semantics via routing to simplify their APIs.
+For example, a user that wants to create a database named "db1" could call:
+
+```http
+PUT https://api.contoso.com/v1.0/databases/db1
+```
+
+In this scenario the databases segment is processing the PUT operation.
+
+Services MAY also use the hybrid defined below.
+
+### 13.2. Stepwise long running operations
+A stepwise operation is one that takes a long, and often unpredictable, length of time to complete, and doesn't offer state transition modeled in the resource.
+This section outlines the approach that services should use to expose such long running operations.
+
+Service MAY expose stepwise operations.
+
+> Stepwise Long Running Operations are sometimes called "Async" operations.
+This causes confusion, as it mixes elements of platforms ("Async / await", "promises", "futures") with elements of API operation.
+This document uses the term "Stepwise Long Running Operation" or often just "Stepwise Operation" to avoid confusion over the word "Async".
+
+Services MUST perform as much synchronous validation as practical on stepwise requests.
+Services MUST prioritize returning errors in a synchronous way, with the goal of having only "Valid" operations processed using the long running operation wire protocol.
+
+For an API that's defined as a Stepwise Long Running Operation the service MUST go through the Stepwise Long Running Operation flow even if the operation can be completed immediately.
+In other words, APIs must adopt and stick with an LRO pattern and not change patterns based on circumstance.
+
+#### 13.2.1. PUT
+Services MAY enable PUT requests for entity creation.
+
+```http
+PUT https://api.contoso.com/v1.0/databases/db1
+```
+
+In this scenario the _databases_ segment is processing the PUT operation.
+
+```http
+HTTP/1.1 202 Accepted
+Operation-Location: https://api.contoso.com/v1.0/operations/123
+```
+
+For services that need to return a 201 Created here, use the hybrid flow described below.
+
+The 202 Accepted should return no body.
+The 201 Created case should return the body of the target resource.
+
+#### 13.2.2. POST
+Services MAY enable POST requests for entity creation.
+
+```http
+POST https://api.contoso.com/v1.0/databases/
+
+{
+ "fileName": "someFile.db",
+ "color": "red"
+}
+```
+
+```http
+HTTP/1.1 202 Accepted
+Operation-Location: https://api.contoso.com/v1.0/operations/123
+```
+
+#### 13.2.3. POST, hybrid model
+Services MAY respond synchronously to POST requests to collections that create a resource even if the resources aren't fully created when the response is generated.
+In order to use this pattern, the response MUST include a representation of the incomplete resource and an indication that it is incomplete.
+
+For example:
+
+```http
+POST https://api.contoso.com/v1.0/databases/ HTTP/1.1
+Host: api.contoso.com
+Content-Type: application/json
+Accept: application/json
+
+{
+ "fileName": "someFile.db",
+ "color": "red"
+}
+```
+
+Service response says the database has been created, but indicates the request is not completed by including the Operation-Location header.
+In this case the status property in the response payload also indicates the operation has not fully completed.
+
+```http
+HTTP/1.1 201 Created
+Location: https://api.contoso.com/v1.0/databases/db1
+Operation-Location: https://api.contoso.com/v1.0/operations/123
+
+{
+ "databaseName": "db1",
+ "color": "red",
+ "Status": "Provisioning",
+ [ … other fields for "database" …]
+}
+```
+
+#### 13.2.4. Operations resource
+Services MAY provide a "/operations" resource at the tenant level.
+
+Services that provide the "/operations" resource MUST provide GET semantics.
+GET MUST enumerate the set of operations, following standard pagination, sorting, and filtering semantics.
+The default sort order for this operation MUST be:
+
+Primary Sort | Secondary Sort
+---------------------- | -----------------------
+Not Started Operations | Operation Creation Time
+Running Operations | Operation Creation Time
+Completed Operations | Operation Creation Time
+
+Note that "Completed Operations" is a goal state (see below), and may actually be any of several different states such as "successful", "cancelled", "failed" and so forth.
+
+#### 13.2.5. Operation resource
+An operation is a user addressable resource that tracks a stepwise long running operation.
+Operations MUST support GET semantics.
+The GET operation against an operation MUST return:
+
+1. The operation resource, it's state, and any extended state relevant to the particular API.
+2. 200 OK as the response code.
+
+Services MAY support operation cancellation by exposing DELETE on the operation.
+If supported DELETE operations MUST be idempotent.
+
+> Note: From an API design perspective, cancellation does not explicitly mean rollback.
+On a per-API defined case it may mean rollback, or compensation, or completion, or partial completion, etc.
+Following a cancelled operation, It SHOULD NOT be a client's responsibility to return the service to a consistent state which allows continued service.
+
+Services that do not support operation cancellation MUST return a 405 Method Not Allowed in the event of a DELETE.
+
+Operations MUST support the following states:
+
+1. NotStarted
+2. Running
+3. Succeeded. Terminal State.
+4. Failed. Terminal State.
+
+Services MAY add additional states, such as "Cancelled" or "Partially Completed". Services that support cancellation MUST sufficiently describe their cancellation such that the state of the system can be accurately determined, and any compensating actions may be run.
+
+Services that support additional states should consider this list of canonical names and avoid creating new names if possible: Cancelling, Cancelled, Aborting, Aborted, Tombstone, Deleting, Deleted.
+
+An operation MUST contain, and provide in the GET response, the following information:
+
+1. The timestamp when the operation was created.
+2. A timestamp for when the current state was entered.
+3. The operation state (notstarted / running / completed).
+
+Services MAY add additional, API specific, fields into the operation.
+The operation status JSON returned looks like:
+
+```json
+{
+ "createdDateTime": "2015-06-19T12-01-03.45Z",
+ "lastActionDateTime": "2015-06-19T12-01-03.45Z",
+ "status": "notstarted | running | succeeded | failed"
+}
+```
+
+##### Percent complete
+Sometimes it is impossible for services to know with any accuracy when an operation will complete.
+Which makes using the Retry-After header problematic.
+In that case, services MAY include, in the operationStatus JSON, a percent complete field.
+
+```json
+{
+ "createdDateTime": "2015-06-19T12-01-03.45Z",
+ "percentComplete": "50",
+ "status": "running"
+}
+```
+
+In this example the server has indicated to the client that the long running operation is 50% complete.
+
+##### Target resource location
+For operations that result in, or manipulate, a resource the service MUST include the target resource location in the status upon operation completion.
+
+```json
+{
+ "createdDateTime": "2015-06-19T12-01-03.45Z",
+ "lastActionDateTime": "2015-06-19T12-06-03.0024Z",
+ "status": "succeeded",
+ "resourceLocation": "https://api.contoso.com/v1.0/databases/db1"
+}
+```
+
+#### 13.2.6. Operation tombstones
+Services MAY choose to support tombstoned operations.
+Services MAY choose to delete tombstones after a service defined period of time.
+
+#### 13.2.7. The typical flow, polling
+- Client invokes a stepwise operation by invoking an action using POST
+- The server MUST indicate the request has been started by responding with a 202 Accepted status code. The response SHOULD include the location header containing a URL that the client should poll for the results after waiting the number of seconds specified in the Retry-After header.
+- Client polls the location until receiving a 200 response with a terminal operation state.
+
+##### Example of the typical flow, polling
+Client invokes the restart action:
+
+```http
+POST https://api.contoso.com/v1.0/databases HTTP/1.1
+Accept: application/json
+
+{
+ "fromFile": "myFile.db",
+ "color": "red"
+}
+```
+
+The server response indicates the request has been created.
+
+```http
+HTTP/1.1 202 Accepted
+Operation-Location: https://api.contoso.com/v1.0/operations/123
+```
+
+Client waits for a period of time then invokes another request to try to get the operation status.
+
+```http
+GET https://api.contoso.com/v1.0/operations/123
+Accept: application/json
+```
+
+Server responds that results are still not ready and optionally provides a recommendation to wait 30 seconds.
+
+```http
+HTTP/1.1 200 OK
+Retry-After: 30
+
+{
+ "createdDateTime": "2015-06-19T12-01-03.4Z",
+ "status": "running"
+}
+```
+
+Client waits the recommended 30 seconds and then invokes another request to get the results of the operation.
+
+```http
+GET https://api.contoso.com/v1.0/operations/123
+Accept: application/json
+```
+
+Server responds with a "status:succeeded" operation that includes the resource location.
+
+```http
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ "createdDateTime": "2015-06-19T12-01-03.45Z",
+ "lastActionDateTime": "2015-06-19T12-06-03.0024Z",
+ "status": "succeeded",
+ "resourceLocation": "https://api.contoso.com/v1.0/databases/db1"
+}
+```
+
+#### 13.2.8. The typical flow, push notifications
+1. Client invokes a long running operation by invoking an action using POST. The client has a push notification already setup on the parent resource.
+2. The service indicates the request has been started by responding with a 202 Accepted status code. The client ignores everything else.
+3. Upon completion of the overall operation the service pushes a notification via the subscription on the parent resource.
+4. The client retrieves the operation result via the resource URL.
+
+##### Example of the typical flow, push notifications existing subscription
+Client invokes the backup action.
+The client already has a push notification subscription setup for db1.
+
+```http
+POST https://api.contoso.com/v1.0/databases/db1?backup HTTP/1.1
+Accept: application/json
+```
+
+The server response indicates the request has been accepted.
+
+```http
+HTTP/1.1 202 Accepted
+Operation-Location: https://api.contoso.com/v1.0/operations/123
+```
+
+The caller ignores all the headers in the return.
+
+The target URL receives a push notification when the operation is complete.
+
+```http
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ "value": [
+ {
+ "subscriptionId": "1234-5678-1111-2222",
+ "context": "subscription context that was specified at setup",
+ "resourceUrl": "https://api.contoso.com/v1.0/databases/db1",
+ "userId" : "contoso.com/user@contoso.com",
+ "tenantId" : "contoso.com"
+ }
+ ]
+}
+```
+
+#### 13.2.9. Retry-After
+In the examples above the Retry-After header indicates the number of seconds that the client should wait before trying to get the result from the URL identified by the location header.
+
+The HTTP specification allows the Retry-After header to alternatively specify a HTTP date, so clients should be prepared to handle this as well.
+
+```http
+HTTP/1.1 202 Accepted
+Operation-Location: http://api.contoso.com/v1.0/operations/123
+Retry-After: 60
+```
+
+Note: The use of the HTTP Date is inconsistent with the use of ISO 8601 Date Format used throughout this document, but is explicitly defined by the HTTP standard in [RFC 7231][rfc-7231-7-1-1-1]. Services SHOULD prefer the integer number of seconds (in decimal) format over the HTTP date format.
+
+### 13.3. Retention policy for operation results
+In some situations, the result of a long running operation is not a resource that can be addressed.
+For example, if you invoke a long running Action that returns a Boolean (rather than a resource).
+In these situations, the Location header points to a place where the Boolean result can be retrieved.
+
+Which begs the question: "How long should operation results be retained?"
+
+A recommended minimum retention time is 24 hours.
+
+Operations SHOULD transition to "tombstone" for an additional period of time prior to being purged from the system.
+
+## 14. Throttling, Quotas, and Limits
+### 14.1. Principles
+Services should be as responsive as possible, so as not to block callers.
+As a rule of thumb any API call that is expected to take longer than 0.5 seconds in the 99th percentile, should consider using the Long-running Operations pattern for those calls.
+Obviously, services cannot guarantee these response times in the face of potentially unlimited load from callers. Services should therefore design and document call request limits for clients, and respond with appropriate, actionable errors and error messages if these limits are exceeded.
+Services should respond quickly with an error when they are generally overloaded, rather than simply respond slowly.
+Finally, many services will have quotas on calls, perhaps a number of operations per hour or day, usually related to a service plan or price.
+When these quotas are exceeded services must also provide immediate, actionable errors.
+Quotas and Limits should be scoped to a customer unit: a subscription, a tenant, an application, a plan, or without any other identification a range of ip addresses…as appropriate to the service goals so that the load is properly shared and one unit is not interfering with another.
+
+### 14.2. Return Codes (429 vs 503)
+HTTP specifies two return codes for these scenarios: '429 Too Many Requests' and '503 Service Unavailable'.
+Services should use 429 for cases where clients are making too many calls and can fix the situation by changing their call pattern.
+Services should respond with 503 in cases where general load or other problems outside the control of the individual callers is responsible for the service becoming slow.
+In all cases, services should also provide information suggesting how long the callers should wait before trying in again.
+Clients should respect these headers and also implement other transient fault handling techniques.
+However, there may be clients that simply retry immediately upon failure, potentially increasing the load on the service.
+To handle this, services should design so that returning 429 or 503 is as inexpensive as possible, either by putting in special fastpath code, or ideally by depending on a common frontdoor or load balancer that provides this functionality.
+
+### 14.3. Retry-After and RateLimit Headers
+The Retry-After header is the standard way for responding to clients who are being throttled.
+It is also common, but optional, in the case of limits and quotas (but not overall system load) to respond with header describing the limit that was exceeded.
+However, services across Microsoft and the industry use a wide range of different headers for this purpose.
+We recommend using three headers to describe the limit, the number of calls remaining under the limit, and the time when the limit will reset.
+However, other headers may be appropriate for specific types of limits. In all cases these must be documented.
+
+### 14.4. Service Guidance
+Services should choose time windows as appropriate for the SLAs or business objectives.
+In the case of Quotas, the Retry-After time and time window may be very long (hours, days, weeks, even months. Services use 429 to indicate the specific caller has made too many calls, and 503 to indicate that the service is load shedding but that it is not the caller’s responsibility.
+
+#### 14.4.1. Responsiveness
+1. Services MUST respond quickly in all circumstances, even when under load.
+2. Calls that take longer than 1s to respond in the 99th percentile SHOULD use the Long-Running Operation pattern
+3. Calls that take longer than 0.5s to respond in the 99th percentile should strongly consider the LRO pattern
+4. Services SHOULD NOT introduce sleeps, pauses, etc. that block callers or are not actionable (“tar-pitting”).
+
+#### 14.4.2. Rate Limits and Quotas
+When a caller has made too many calls
+
+1. Services MUST return a 429 code
+2. Services MUST return a standard error response describing the specifics so that a programmer can make appropriate changes
+3. Services MUST return a Retry-After header that indicates how long clients should wait before retrying
+4. Services MAY return RateLimit headers that document the limit or quota that has been exceeded
+5. Services MAY return RateLimit-Limit: the number of calls the client is allowed to make in a time window
+6. Services MAY return RateLimit-Remaining: the number of calls remaining in the time window
+7. Services MAY return RateLimit-Reset: the time at which the window resets in UTC epoch seconds
+8. Services MAY return other service specific RateLimit headers as appropriate for more detailed information or specific limits or quotas
+
+#### 14.4.3. Overloaded services
+When services are generally overloaded and load shedding
+
+1. Services MUST Return a 503 code
+2. Services MUST Return a standard error response (see 7.10.2) describing the specifics so that a programmer can make appropriate changes
+3. Services MUST Return a Retry-After header that indicates how long clients should wait before retrying
+4. In the 503 case, the service SHOULD NOT return RateLimit headers
+
+#### 14.4.4. Example Response
+
+```http
+HTTP/1.1 429 Too Many Requests
+Content-Type: application/json
+Retry-After: 5
+RateLimit-Limit: 1000
+RateLimit-Remaining: 0
+RateLimit-Reset: 1538152773
+{
+ "error": {
+ "code": "requestLimitExceeded",
+ "message": "The caller has made too many requests in the time period.",
+ "details": {
+ "code": "RateLimit",
+ "limit": "1000",
+ "remaining": "0",
+ "reset": "1538152773",
+ }
+ }
+}
+```
+
+### 14.5. Caller Guidance
+Callers include all users of the API: tools, portals, other services, not just user clients
+
+1. Callers MUST wait for a minimum of time indicated in a response with a Retry-After before retrying a request.
+2. Callers MAY assume that request is retriable after receiving a response with a Retry-After header without making any changes to the request.
+3. Clients SHOULD use shared SDKs and common transient fault libraries to implement the proper behavior
+
+See: https://docs.microsoft.com/en-us/azure/architecture/best-practices/transient-faults
+
+### 14.6. Handling callers that ignore Retry-After headers
+Ideally, 429 and 503 returns are so low cost that even clients that retry immediately can be handled.
+In these cases, if possible the service team should make an effort to contact or fix the client.
+If it is a known partner, a bug or incident should be filed.
+In extreme cases it may be necessary to use DoS style protections such as blocking the caller.
+
+## 15. Push notifications via webhooks
+### 15.1. Scope
+Services MAY implement push notifications via web hooks.
+This section addresses the following key scenario:
+
+> Push notification via HTTP Callbacks, often called Web Hooks, to publicly-addressable servers.
+
+The approach set forth is chosen due to its simplicity, broad applicability, and low barrier to entry for service subscribers.
+It's intended as a minimal set of requirements and as a starting point for additional functionality.
+
+### 15.2. Principles
+The core principles for services that support web hooks are:
+
+1. Services MUST implement at least a poke/pull model. In the poke/pull model, a notification is sent to a client, and clients then send a request to get the current state or the record of change since their last notification. This approach avoids complexities around message ordering, missed messages, and change sets. Services MAY add more data to provide rich notifications.
+2. Services MUST implement the challenge/response protocol for configuring callback URLs.
+3. Services SHOULD have a recommended age-out period, with flexibility for services to vary based on scenario.
+4. Services SHOULD allow subscriptions that are raising successful notifications to live forever and SHOULD be tolerant of reasonable outage periods.
+5. Firehose subscriptions MUST be delivered only over HTTPS. Services SHOULD require other subscription types to be HTTPS. See the "Security" section for more details.
+
+### 15.3. Types of subscriptions
+There are two subscription types, and services MAY implement either, both, or none.
+The supported subscription types are:
+
+1. Firehose subscriptions – a subscription is manually created for the subscribing application, typically in an app registration portal. Notifications of activity that any users have consented to the app receiving are sent to this single subscription.
+2. Per-resource subscriptions – the subscribing application uses code to programmatically create a subscription at runtime for some user-specific entity(s).
+
+Services that support both subscription types SHOULD provide differentiated developer experiences for the two types:
+
+1. Firehose – Services MUST NOT require developers to create code except to directly verify and respond to notifications. Services MUST provide administrative UI for subscription management. Services SHOULD NOT assume that end users are aware of the subscription, only the subscribing application's functionality.
+2. Per-user – Services MUST provide an API for developers to create and manage subscriptions as part of their app as well as verifying and responding to notifications. Services MAY expect end users to be aware of subscriptions and MUST allow end users to revoke subscriptions where they were created directly in response to user actions.
+
+### 15.4. Call sequences
+The call sequence for a firehose subscription MUST follow the diagram below.
+It shows manual registration of application and subscription, and then the end user making use of one of the service's APIs.
+At this part of the flow, two things MUST be stored:
+
+1. The service MUST store the end user's act of consent to receiving notifications from this specific application (typically a background usage OAUTH scope.)
+2. The subscribing application MUST store the end user's tokens in order to call back for details once notified of changes.
+
+The final part of the sequence is the notification flow itself.
+
+Non-normative implementation guidance: A resource in the service changes and the service needs to run the following logic:
+
+1. Determine the set of users who have access to the resource, and could thus expect apps to receive notifications about it on their behalf.
+2. See which of those users have consented to receiving notifications and from which apps.
+3. See which apps have registered a firehose subscription.
+4. Join 1, 2, 3 to produce the concrete set of notifications that must be sent to apps.
+
+It should be noted that the act of user consent and the act of setting up a firehose subscription could arrive in either order.
+Services SHOULD send notifications with setup processed in either order.
+
+![Firehose subscription setup][websequencediagram-firehose-subscription-setup]
+
+For a per-user subscription, app registration is either manual or automated.
+The call flow for a per-user subscription MUST follow the diagram below.
+It shows the end user making use of one of the service's APIs, and again, the same two things MUST be stored:
+
+1. The service MUST store the end user's act of consent to receiving notifications from this specific application (typically a background usage OAUTH scope).
+2. The subscribing application MUST store the end user's tokens in order to call back for details once notified of changes.
+
+In this case, the subscription is set up programmatically using the end-user's token from the subscribing application.
+The app MUST store the ID of the registered subscription alongside the user tokens.
+
+Non normative implementation guidance: In the final part of the sequence, when an item of data in the service changes and the service needs to run the following logic:
+
+1. Find the set of subscriptions that correspond via resource to the data that changed.
+2. For subscriptions created under an app+user token, send a notification to the app per subscription with the subscription ID and user id of the subscription-creator.
+- For subscriptions created with an app only token, check that the owner of the changed data or any user that has visibility of the changed data has consented to notifications to the application, and if so send a set of notifications per user id to the app per subscription with the subscription ID.
+
+ ![User subscription setup][websequencediagram-user-subscription-setup]
+
+### 15.5. Verifying subscriptions
+When subscriptions change either programmatically or in response to change via administrative UI portals, the subscribing service needs to be protected from malicious or unexpected calls from services pushing potentially large volumes of notification traffic.
+
+For all subscriptions, whether firehose or per-user, services MUST send a verification request as part of creation or modification via portal UI or API request, before sending any other notifications.
+
+Verification requests MUST be of the following format as an HTTP/HTTPS POST to the subscription's _notificationUrl_.
+
+```http
+POST https://{notificationUrl}?validationToken={randomString}
+ClientState: clientOriginatedOpaqueToken (if provided by client on subscription-creation)
+Content-Length: 0
+```
+
+For the subscription to be set up, the application MUST respond with 200 OK to this request, with the _validationToken_ value as the sole entity body.
+Note that if the _notificationUrl_ contains query parameters, the _validationToken_ parameter must be appended with an `&`.
+
+If any challenge request does not receive the prescribed response within 5 seconds of sending the request, the service MUST return an error, MUST NOT create the subscription, and MUST NOT send further requests or notifications to _notificationUrl_.
+
+Services MAY perform additional validations on URL ownership.
+
+### 15.6. Receiving notifications
+Services SHOULD send notifications in response to service data changes that do not include details of the changes themselves, but include enough information for the subscribing application to respond appropriately to the following process:
+
+1. Applications MUST identify the correct cached OAuth token to use for a callback
+2. Applications MAY look up any previous delta token for the relevant scope of change
+3. Applications MUST determine the URL to call to perform the relevant query for the new state of the service, which MAY be a delta query.
+
+Services that are providing notifications that will be relayed to end users MAY choose to add more detail to notification packets in order to reduce incoming call load on their service.
+ Such services MUST be clear that notifications are not guaranteed to be delivered and may be lossy or out of order.
+
+Notifications MAY be aggregated and sent in batches.
+Applications MUST be prepared to receive multiple events inside a single push notification.
+
+The service MUST send all Web Hook data notifications as POST requests.
+
+Services MUST allow for a 30-second timeout for notifications.
+If a timeout occurs or the application responds with a 5xx response, then the service SHOULD retry the notification with exponential back-off.
+All other responses will be ignored.
+
+The service MUST NOT follow 301/302 redirect requests.
+
+#### 15.6.1. Notification payload
+The basic format for notification payloads is a list of events, each containing the id of the subscription whose referenced resources have changed, the type of change, the resource that should be consumed to identify the exact details of the change and sufficient identity information to look up the token required to call that resource.
+
+For a firehose subscription, a concrete example of this may look like:
+
+```json
+{
+ "value": [
+ {
+ "subscriptionId": "32b8cbd6174ab18b",
+ "resource": "https://api.contoso.com/v1.0/users/user@contoso.com/files?$delta",
+ "userId" : "",
+ "tenantId" : ""
+ }
+ ]
+}
+```
+
+For a per-user subscription, a concrete example of this may look like:
+
+```json
+{
+ "value": [
+ {
+ "subscriptionId": "32b8cbd6174ab183",
+ "clientState": "clientOriginatedOpaqueToken",
+ "expirationDateTime": "2016-02-04T11:23Z",
+ "resource": "https://api.contoso.com/v1.0/users/user@contoso.com/files/$delta",
+ "userId" : "",
+ "tenantId" : ""
+ },
+ {
+ "subscriptionId": "97b391179fa22",
+ "clientState ": "clientOriginatedOpaqueToken",
+ "expirationDateTime": "2016-02-04T11:23Z",
+ "resource": "https://api.contoso.com/v1.0/users/user@contoso.com/files/$delta",
+ "userId" : "",
+ "tenantId" : ""
+ }
+ ]
+}
+```
+
+Following is a detailed description of the JSON payload.
+
+A notification item consists a top-level object that contains an array of events, each of which identified the subscription due to which this notification is being sent.
+
+Field | Description
+----- | --------------------------------------------------------------------------------------------------
+value | Array of events that have been raised within the subscription’s scope since the last notification.
+
+Each item of the events array contains the following properties:
+
+Field | Description
+------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+subscriptionId | The id of the subscription due to which this notification has been sent. Services MUST provide the *subscriptionId* field.
+clientState | Services MUST provide the *clientState* field if it was provided at subscription creation time.
+expirationDateTime | Services MUST provide the *expirationDateTime* field if the subscription has one.
+resource | Services MUST provide the resource field. This URL MUST be considered opaque by the subscribing application. In the case of a richer notification it MAY be subsumed by message content that implicitly contains the resource URL to avoid duplication. If a service is providing this data as part of a more detailed data packet, then it need not be duplicated.
+userId | Services MUST provide this field for user-scoped resources. In the case of user-scoped resources, the unique identifier for the user should be used. In the case of resources shared between a specific set of users, multiple notifications must be sent, passing the unique identifier of each user. For tenant-scoped resources, the user id of the subscription should be used.
+tenantId | Services that wish to support cross-tenant requests SHOULD provide this field. Services that provide notifications on tenant-scoped data MUST send this field.
+
+### 15.7. Managing subscriptions programmatically
+For per-user subscriptions, an API MUST be provided to create and manage subscriptions.
+The API must support at least the operations described here.
+
+#### 15.7.1. Creating subscriptions
+A client creates a subscription by issuing a POST request against the subscriptions resource.
+The subscription namespace is client-defined via the POST operation.
+
+```
+https://api.contoso.com/apiVersion/$subscriptions
+```
+
+The POST request contains a single subscription object to be created.
+That subscription object has the following properties:
+
+Property Name | Required | Notes
+--------------- | -------- | ---------------------------------------------------------------------------------------------------------------------------
+resource | Yes | Resource path to watch.
+notificationUrl | Yes | The target web hook URL.
+clientState | No | Opaque string passed back to the client on all notifications. Callers may choose to use this to provide tagging mechanisms.
+
+If the subscription was successfully created, the service MUST respond with the status code 201 CREATED and a body containing at least the following properties:
+
+Property Name | Required | Notes
+------------------ | -------- | -------------------------------------------------------------------------------------------
+id | Yes | Unique ID of the new subscription that can be used later to update/delete the subscription.
+expirationDateTime | No | Uses existing Microsoft REST API Guidelines defined time formats.
+
+Creation of subscriptions SHOULD be idempotent.
+The combination of properties scoped to the auth token, provides a uniqueness constraint.
+
+Below is an example request using a User + Application principal to subscribe to notifications from a file:
+
+```http
+POST https://api.contoso.com/files/v1.0/$subscriptions HTTP 1.1
+Authorization: Bearer {UserPrincipalBearerToken}
+
+{
+ "resource": "http://api.service.com/v1.0/files/file1.txt",
+ "notificationUrl": "https://contoso.com/myCallbacks",
+ "clientState": "clientOriginatedOpaqueToken"
+}
+```
+
+The service SHOULD respond to such a message with a response format minimally like this:
+
+```json
+{
+ "id": "32b8cbd6174ab18b",
+ "expirationDateTime": "2016-02-04T11:23Z"
+}
+```
+
+Below is an example using an Application-Only principal where the application is watching all files to which it's authorized:
+
+```http
+POST https://api.contoso.com/files/v1.0/$subscriptions HTTP 1.1
+Authorization: Bearer {ApplicationPrincipalBearerToken}
+
+{
+ "resource": "All.Files",
+ "notificationUrl": "https://contoso.com/myCallbacks",
+ "clientState": "clientOriginatedOpaqueToken"
+}
+```
+
+The service SHOULD respond to such a message with a response format minimally like this:
+
+```json
+{
+ "id": "8cbd6174abb391179",
+ "expirationDateTime": "2016-02-04T11:23Z"
+}
+```
+
+#### 15.7.2. Updating subscriptions
+Services MAY support amending subscriptions.
+ To update the properties of an existing subscription, clients use PATCH requests providing the ID and the properties that need to change.
+Omitted properties will retain their values.
+To delete a property, assign a value of JSON null to it.
+
+As with creation, subscriptions are individually managed.
+
+The following request changes the notification URL of an existing subscription:
+
+```http
+PATCH https://api.contoso.com/files/v1.0/$subscriptions/{id} HTTP 1.1
+Authorization: Bearer {UserPrincipalBearerToken}
+
+{
+ "notificationUrl": "https://contoso.com/myNewCallback"
+}
+```
+
+If the PATCH request contains a new _notificationUrl_, the server MUST perform validation on it as described above.
+If the new URL fails to validate, the service MUST fail the PATCH request and leave the subscription in its previous state.
+
+The service MUST return an empty body and `204 No Content` to indicate a successful patch.
+
+The service MUST return an error body and status code if the patch failed.
+
+The operation MUST succeed or fail atomically.
+
+#### 15.7.3. Deleting subscriptions
+Services MUST support deleting subscriptions.
+Existing subscriptions can be deleted by making a DELETE request against the subscription resource:
+
+```http
+DELETE https://api.contoso.com/files/v1.0/$subscriptions/{id} HTTP 1.1
+Authorization: Bearer {UserPrincipalBearerToken}
+```
+
+As with update, the service MUST return `204 No Content` for a successful delete, or an error body and status code to indicate failure.
+
+#### 15.7.4. Enumerating subscriptions
+To get a list of active subscriptions, clients issue a GET request against the subscriptions resource using a User + Application or Application-Only bearer token:
+
+```http
+GET https://api.contoso.com/files/v1.0/$subscriptions HTTP 1.1
+Authorization: Bearer {UserPrincipalBearerToken}
+```
+
+The service MUST return a format as below using a User + Application principal bearer token:
+
+```json
+{
+ "value": [
+ {
+ "id": "32b8cbd6174ab18b",
+ "resource": " http://api.contoso.com/v1.0/files/file1.txt",
+ "notificationUrl": "https://contoso.com/myCallbacks",
+ "clientState": "clientOriginatedOpaqueToken",
+ "expirationDateTime": "2016-02-04T11:23Z"
+ }
+ ]
+}
+```
+
+An example that may be returned using Application-Only principal bearer token:
+
+```json
+{
+ "value": [
+ {
+ "id": "6174ab18bfa22",
+ "resource": "All.Files ",
+ "notificationUrl": "https://contoso.com/myCallbacks",
+ "clientState": "clientOriginatedOpaqueToken",
+ "expirationDateTime": "2016-02-04T11:23Z"
+ }
+ ]
+}
+```
+
+### 15.8. Security
+All service URLs must be HTTPS (that is, all inbound calls MUST be HTTPS). Services that deal with Web Hooks MUST accept HTTPS.
+
+We recommend that services that allow client defined Web Hook Callback URLs SHOULD NOT transmit data over HTTP.
+This is because information can be inadvertently exposed via client, network, server logs and other mechanisms.
+
+However, there are scenarios where the above recommendations cannot be followed due to client endpoint or software limitations.
+Consequently, services MAY allow web hook URLs that are HTTP.
+
+Furthermore, services that allow client defined HTTP web hooks callback URLs SHOULD be compliant with privacy policy specified by engineering leadership.
+This will typically include recommending that clients prefer SSL connections and adhere to special precautions to ensure that logs and other service data collection are properly handled.
+
+For example, services may not want to require developers to generate certificates to onboard.
+Services might only enable this on test accounts.
+
+## 16. Unsupported requests
+RESTful API clients MAY request functionality that is currently unsupported.
+RESTful APIs MUST respond to valid but unsupported requests consistent with this section.
+
+### 16.1. Essential guidance
+RESTful APIs will often choose to limit functionality that can be performed by clients.
+For instance, auditing systems allow records to be created but not modified or deleted.
+Similarly, some APIs will expose collections but require or otherwise limit filtering and ordering criteria, or MAY not support client-driven pagination.
+
+### 16.2. Feature allow list
+If a service does not support any of the below API features, then an error response MUST be provided if the feature is requested by a caller.
+The features are:
+- Key Addressing in a collection, such as: `https://api.contoso.com/v1.0/people/user1@contoso.com`
+- Filtering a collection by a property value, such as: `https://api.contoso.com/v1.0/people?$filter=name eq 'david'`
+- Filtering a collection by range, such as: `http://api.contoso.com/v1.0/people?$filter=hireDate ge 2014-01-01 and hireDate le 2014-12-31`
+- Client-driven pagination via $top and $skip, such as: `http://api.contoso.com/v1.0/people?$top=5&$skip=2`
+- Sorting by $orderBy, such as: `https://api.contoso.com/v1.0/people?$orderBy=name desc`
+- Providing $delta tokens, such as: `https://api.contoso.com/v1.0/people?$delta`
+
+#### 16.2.1. Error response
+Services MUST provide an error response if a caller requests an unsupported feature found in the feature allow list.
+The error response MUST be an HTTP status code from the 4xx series, indicating that the request cannot be fulfilled.
+Unless a more specific error status is appropriate for the given request, services SHOULD return "400 Bad Request" and an error payload conforming to the error response guidance provided in the Microsoft REST API Guidelines.
+Services SHOULD include enough detail in the response message for a developer to determine exactly what portion of the request is not supported.
+
+Example:
+
+```http
+GET https://api.contoso.com/v1.0/people?$orderBy=name HTTP/1.1
+Accept: application/json
+```
+
+```http
+HTTP/1.1 400 Bad Request
+Content-Type: application/json
+
+{
+ "error": {
+ "code": "ErrorUnsupportedOrderBy",
+ "message": "Ordering by name is not supported."
+ }
+}
+```
+
+## 17. Naming guidelines
+### 17.1. Approach
+Naming policies should aid developers in discovering functionality without having to constantly refer to documentation.
+Use of common patterns and standard conventions greatly aids developers in correctly guessing common property names and meanings.
+Services SHOULD use verbose naming patterns and SHOULD NOT use abbreviations other than acronyms that are the dominant mode of expression in the domain being represented by the API, (e.g. Url).
+
+### 17.2. Casing
+- Acronyms SHOULD follow the casing conventions as though they were regular words (e.g. Url).
+- All identifiers including namespaces, entityTypes, entitySets, properties, actions, functions and enumeration values SHOULD use lowerCamelCase.
+- HTTP headers are the exception and SHOULD use standard HTTP convention of Capitalized-Hyphenated-Terms.
+
+### 17.3. Names to avoid
+Certain names are so overloaded in API domains that they lose all meaning or clash with other common usages in domains that cannot be avoided when using REST APIs, such as OAUTH.
+Services SHOULD NOT use the following names:
+- Context
+- Scope
+- Resource
+
+### 17.4. Forming compound names
+- Services SHOULD avoid using articles such as 'a', 'the', 'of' unless needed to convey meaning.
+ - e.g. names such as aUser, theAccount, countOfBooks SHOULD NOT be used, rather user, account, bookCount SHOULD be preferred.
+- Services SHOULD add a type to a property name when not doing so would cause ambiguity about how the data is represented or would cause the service not to use a common property name.
+- When adding a type to a property name, services MUST add the type at the end, e.g. createdDateTime.
+
+### 17.5. Identity properties
+- Services MUST use string types for identity properties.
+- For OData services, the service MUST use the OData @id property to represent the canonical identifier of the resource.
+- Services MAY use the simple 'id' property to represent a local or legacy primary key value for a resource.
+- Services SHOULD use the name of the relationship postfixed with 'Id' to represent a foreign key to another resource, e.g. subscriptionId.
+ - The content of this property SHOULD be the canonical ID of the referenced resource.
+
+### 17.6. Date and time properties
+
+- For properties requiring both date and time, services MUST use the suffix 'DateTime'.
+- For properties requiring only date information without specifying time, services MUST use the suffix 'Date', e.g. birthDate.
+- For properties requiring only time information without specifying date, services MUST use the suffix 'Time', e.g. appointmentStartTime.
+
+### 17.7. Name properties
+- For the overall name of a resource typically shown to users, services MUST use the property name 'displayName'.
+- Services MAY use other common naming properties, e.g. givenName, surname, signInName.
+
+### 17.8. Collections and counts
+- Services MUST name collections as plural nouns or plural noun phrases using correct English.
+- Services MAY use simplified English for nouns that have plurals not in common verbal usage.
+ - e.g. schemas MAY be used instead of schemata.
+- Services MUST name counts of resources with a noun or noun phrase suffixed with 'Count'.
+
+### 17.9. Common property names
+Where services have a property, whose data matches the names below, the service MUST use the name from this table.
+This table will grow as services add terms that will be more commonly used.
+Service owners adding such terms SHOULD propose additions to this document.
+
+| |
+|------------- |
+ attendees |
+ body |
+ createdDateTime |
+ childCount |
+ children |
+ contentUrl |
+ country |
+ createdBy |
+ displayName |
+ errorUrl |
+ eTag |
+ event |
+ expirationDateTime |
+ givenName |
+ jobTitle |
+ kind |
+ id |
+ lastModifiedDateTime |
+ location |
+ memberOf |
+ message |
+ name |
+ owner |
+ people |
+ person |
+ postalCode |
+ photo |
+ preferredLanguage |
+ properties |
+ signInName |
+ surname |
+ tags |
+ userPrincipalName |
+ webUrl |
+
+## 18. Appendix
+### 18.1. Sequence diagram notes
+All sequence diagrams in this document are generated using the [WebSequenceDiagrams.com](https://www.websequencediagrams.com/). To generate them, paste the text below into the web tool.
+
+#### 18.1.1. Push notifications, per user flow
+
+```
+=== Begin Text ===
+note over Developer, Automation, App Server:
+ An App Developer like MovieMaker
+ Wants to integrate with primary service like Dropbox
+end note
+note over DB Portal, DB App Registration, DB Notifications, DB Auth, DB Service: The primary service like Dropbox
+note over Client: The end users' browser or installed app
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Manual App Registration
+
+
+Developer <--> DB Portal : Login into Portal, App Registration UX
+DB Portal -> +DB App Registration: App Name etc.
+note over DB App Registration: Confirm Portal Access Token
+
+DB App Registration -> -DB Portal: App ID
+DB Portal <--> App Server: Developer copies App ID
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Manual Notification Registration
+
+Developer <--> DB Portal: webhook registration UX
+DB Portal -> +DB Notifications: Register: App Server webhook URL, Scope, App ID
+Note over DB Notifications : Confirm Portal Access Token
+DB Notifications -> -DB Portal: notification ID
+DB Portal --> App Server : Developer may copy notification ID
+
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Client Authorization
+
+Client -> +App Server : Request access to DB protected information
+App Server -> -Client : Redirect to DB Authorization endpoint with authorization request
+Client -> +DB Auth : Redirected authorization request
+Client <--> DB Auth : Authorization UX
+DB Auth -> -Client : Redirect back to App Server with code
+Client -> +App Server : Redirect request back to access server with access code
+App Server -> +DB Auth : Request tokens with access code
+note right of DB Service: Cache that this User ID provided access to App ID
+DB Auth -> -App Server : Response with access, refresh, and ID tokens
+note right of App Server : Cache tokens by user ID
+App Server -> -Client : Return information to client
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Notification Flow
+
+Client <--> DB Service: Changes to user data - typical via interacting with App Server via Client
+DB Service -> App Server : Notification with notification ID and user ID
+App Server -> +DB Service : Request changed information with cached access tokens and "since" token
+note over DB Service: Confirm User Access Token
+DB Service -> -App Server : Response with data and new "since" token
+note right of App Server: Update status and cache new "since" token
+=== End Text ===
+```
+
+#### 18.1.2. Push notifications, firehose flow
+
+```
+=== Begin Text ===
+note over Developer, Automation, App Server:
+ An App Developer like MovieMaker
+ Wants to integrate with primary service like Dropbox
+end note
+note over DB Portal, DB App Registration, DB Notifications, DB Auth, DB Service: The primary service like Dropbox
+note over Client: The end users' browser or installed app
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : App Registration
+
+alt Automated app registration
+ Developer <--> Automation: Configure
+ Automation -> +DB App Registration: App Name etc.
+ note over DB App Registration: Confirm App Access Token
+ DB App Registration -> -Automation: App ID, App Secret
+ Automation --> App Server : Embed App ID, App Secret
+else Manual app registration
+ Developer <--> DB Portal : Login into Portal, App Registration UX
+ DB Portal -> +DB App Registration: App Name etc.
+ note over DB App Registration: Confirm Portal Access Token
+
+ DB App Registration -> -DB Portal: App ID
+ DB Portal <--> App Server: Developer copies App ID
+end
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Client Authorization
+
+Client -> +App Server : Request access to DB protected information
+App Server -> -Client : Redirect to DB Authorization endpoint with authorization request
+Client -> +DB Auth : Redirected authorization request
+Client <--> DB Auth : Authorization UX
+DB Auth -> -Client : Redirect back to App Server with code
+Client -> +App Server : Redirect request back to access server with access code
+App Server -> +DB Auth : Request tokens with access code
+note right of DB Service: Cache that this User ID provided access to App ID
+DB Auth -> -App Server : Response with access, refresh, and ID tokens
+note right of App Server : Cache tokens by user ID
+App Server -> -Client : Return information to client
+
+
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Notification Registration
+
+App Server->+DB Notifications: Register: App server webhook URL, Scope, App ID
+note over DB Notifications : Confirm User Access Token
+DB Notifications -> -App Server: notification ID
+note right of App Server : Cache the Notification ID and User Access Token
+
+
+
+note over Developer, Automation, App Server, DB Portal, DB App Registration, DB Notifications, Client : Notification Flow
+
+Client <--> DB Service: Changes to user data - typical via interacting with App Server via Client
+DB Service -> App Server : Notification with notification ID and user ID
+App Server -> +DB Service : Request changed information with cached access tokens and "since" token
+note over DB Service: Confirm User Access Token
+DB Service -> -App Server : Response with data and new "since" token
+note right of App Server: Update status and cache new "since" token
+
+
+
+=== End Text ===
+```
+[fielding]: https://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm
+[IANA-headers]: https://www.iana.org/assignments/message-headers/message-headers.xhtml
+[rfc-2119]: https://tools.ietf.org/html/rfc2119
+[rfc7231-7-1-1-1]: https://tools.ietf.org/html/rfc7231#section-7.1.1.1
+[rfc-7230-3-1-1]: https://tools.ietf.org/html/rfc7230#section-3.1.1
+[rfc-7231]: https://tools.ietf.org/html/rfc7231
+[rest-in-practice]: https://www.amazon.com/REST-Practice-Hypermedia-Systems-Architecture/dp/0596805829/
+[rest-on-wikipedia]: https://en.wikipedia.org/wiki/Representational_state_transfer
+[rfc-5789]: https://tools.ietf.org/html/rfc5789
+[rfc-5988]: https://tools.ietf.org/html/rfc5988
+[rfc-3339]: https://tools.ietf.org/html/rfc3339
+[rfc-5322-3-3]: https://tools.ietf.org/html/rfc5322#section-3.3
+[cors-preflight]: https://www.w3.org/TR/cors/#resource-preflight-requests
+[rfc-3864]: https://tools.ietf.org/html/rfc3864
+[odata-json-annotations]: https://docs.oasis-open.org/odata/odata-json-format/v4.0/os/odata-json-format-v4.0-os.html#_Instance_Annotations
+[cors]: https://www.w3.org/TR/access-control/
+[cors-user-credentials]: https://www.w3.org/TR/access-control/#user-credentials
+[cors-simple-headers]: https://www.w3.org/TR/access-control/#simple-header
+[rfc-4627]: https://tools.ietf.org/html/rfc4627
+[iso-8601]: https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.15
+[clr-time]: https://msdn.microsoft.com/en-us/library/System.DateTime(v=vs.110).aspx
+[ecmascript-time]: https://www.ecma-international.org/ecma-262/5.1/#sec-15.9.1.1
+[ole-date]: https://docs.microsoft.com/en-us/windows/desktop/api/oleauto/nf-oleauto-varianttimetosystemtime
+[ticks-time]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms724290(v=vs.85).aspx
+[unix-time]: https://msdn.microsoft.com/en-us/library/1f4c8f33.aspx
+[windows-time]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms724290(v=vs.85).aspx
+[excel-time]: https://support.microsoft.com/kb/214326?wa=wsignin1.0
+[wikipedia-iso8601-durations]: https://en.wikipedia.org/wiki/ISO_8601#Durations
+[wikipedia-iso8601-intervals]: https://en.wikipedia.org/wiki/ISO_8601#Time_intervals
+[wikipedia-iso8601-repeatingintervals]: https://en.wikipedia.org/wiki/ISO_8601#Repeating_intervals
+[principle-of-least-astonishment]: https://en.wikipedia.org/wiki/Principle_of_least_astonishment
+[odata-breaking-changes]: https://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398209
+[websequencediagram-firehose-subscription-setup]: https://www.websequencediagrams.com/cgi-bin/cdraw?lz=bm90ZSBvdmVyIERldmVsb3BlciwgQXV0b21hdGlvbiwgQXBwIFNlcnZlcjogCiAgICAgQW4AEAUAJwkgbGlrZSBNb3ZpZU1ha2VyACAGV2FudHMgdG8gaW50ZWdyYXRlIHdpdGggcHJpbWFyeSBzZXJ2aWNlADcGRHJvcGJveAplbmQgbm90ZQoAgQwLQiBQb3J0YWwsIERCAIEJBVJlZ2lzdHIAgRkHREIgTm90aWZpYwCBLAVzACEGdXRoACsFUwBgBjogVGhlAF0eAIF_CkNsaWVudAAtBmVuZCB1c2VycycgYnJvd3NlciBvciBpbnN0YWxsZWQgYXBwCgCBIQwAgiQgAIFABQCBIS8AgQoGIDogTWFudWFsAIFzEQoKCgCDAgo8LS0-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-B3MAPgsAglEHAEsFAIIzDgCBXw0Agn8GdG9rZW5zACcSAI0_BXJpZ2h0IG9mAItpDUNhY2hlIHRoYXQgdGhpcyBVc2VyIElEIHByb3ZpZGVkAINNCwCIZgoAggcJAIN7D3Nwb25zAI0_BwCECgYsIHJlZnJlc2gsIGFuZCBJRACBHAcAgQMPAIYADQCBDAcAgUUGYnkAjFkFIElEAIQkG3R1cm4AhF4MIHRvIGMAjR8FAIwRagCJVw1GbG93AIYqCQCMaQgAgmoKaGFuZ2UAj3YFAIFXBWRhdGEgLSB0eXBpY2FsIHZpYQCQDgVyYWN0aW5nAJAPBgCJQQt2aWEAjnsHCgCPNgogAIhDEACKZw0AkFMFAIkBDwCDDAUAgkYWKwBNCwCHWApjAIEyBQCHRg0AhWUHYWNoAIQeDACEfwVhbmQgInNpbmNlIgCFEQYAkSQOAIR3CgCNfwcAhHQFAIpQEACBUgsAhFAcAII8BWFuZCBuZXcAYRQAhFUTOiBVcGRhdGUgc3RhdHUAgSkGAIFDBQAxEwoKCg&s=mscgen
+[websequencediagram-user-subscription-setup]: https://www.websequencediagrams.com/cgi-bin/cdraw?lz=bm90ZSBvdmVyIERldmVsb3BlciwgQXV0b21hdGlvbiwgQXBwIFNlcnZlcjogCiAgICAgQW4AEAUAJwkgbGlrZSBNb3ZpZU1ha2VyACAGV2FudHMgdG8gaW50ZWdyYXRlIHdpdGggcHJpbWFyeSBzZXJ2aWNlADcGRHJvcGJveAplbmQgbm90ZQoAgQwLQiBQb3J0YWwsIERCAIEJBVJlZ2lzdHIAgRkHREIgTm90aWZpYwCBLAVzACEGdXRoACsFUwBgBjogVGhlAF0eAIF_CkNsaWVudAAtBmVuZCB1c2VycycgYnJvd3NlciBvciBpbnN0YWxsZWQgYXBwCgCBIQwAgiQgAIFABQCBIS8AgQoGIDoAgWwRCgphbHQAgyUIAIEHBiByABQMICAAgxsLPC0tPgCDTws6IENvbmZpZ3VyZQogIACDaAsgLT4gKwCCWBMAegZOYW1lIGV0Yy4AhAgFAIMaDQAfEgBdBXJtAIQ_BUFjY2VzcyBUb2tlAIETBgCDOxIgLT4gLQCBFgxBcHAgSUQAhHwIY3JldACBGxAtPgCFFgsgOiBFbWJlZAAkFGVsc2UgTWFudWFsAIIEJACEbQkgOiBMb2dpbiBpbnRvAIUBCQCBKRFVWACGGAUALQoAgh8mAIIZKwCBCAcAgjoNAIIsHACGLwkAgj8IAIESDgCECAYAh1ELAIdFCmNvcGllcwAuCGVuZACEeGoAhWQHQXV0aG9yaXoAhV8HAIV6By0-ICsAg2ANUmVxdWVzdCBhAIRVBnRvIERCIHByb3RlY3RlZCBpbmZvcgCJQQYKAIQaCy0-IC0AhkoJUmVkaXJlY3QANgcAbA0gZW5kcG9pbnQAiTMGYQAPDXIAdgYAgRAMAIhxBwBLC2VkABgeAIRjCAAwB0EAcQxVWAoASQgAgRwWYmFjayB0bwCFdAwAilwFY29kZQCCGRppAIFpBwCBOQcAPQkAgj0HcwA-CwCCUAcASwUAgjIOAIFeDQCCfgZ0b2tlbnMAJxIAjFsFcmlnaHQgb2YAiwUNQ2FjaGUgdGhhdCB0aGlzIFVzZXIgSUQgcHJvdmlkZWQAg0wLAIU6BwCCBAwAg3oPc3BvbnMAjFsHAIQJBiwgcmVmcmVzaCwgYW5kIElEAIEcBwCBAw8AiDENAIEMBwCBRQZieQCLdQUgSUQAhCMbdHVybgCEXQwgdG8gYwCMOwUKCgCLL2oAjXUMAIwTDwCPNQotPisAjhwQOgCORQdlcgCMVwYAg3YIZWJob29rIFVSTCwgU2NvcGUAkAEGSUQAjwoOAI5rDSAAi2UKAINFBQCLYw0AHBEAgzUOOiBuAIE2DABgCACDCB1oZQCBaQ5JRACDYwUAahIAghB4RmxvdwCJMwkAjE0IAIV0CmhhbmdlAJIcBQCEYQVkYXRhIC0gdHlwaWNhbCB2aWEAkjQFcmFjdGluZwCSNQYAjV8LdmlhAJEhBwoAkVwKIACNfhAAhAsNAJJ5BQCCWQ8AhhYFAIVQFisATQsAimEKYwCBMgUAik8NAIhvB2FjaACHKAwAiAkFYW5kICJzaW5jZSIAiBsGAJNKDgCIAQoAhB0cAIFSCwCHWhwAgjwFYW5kIG5ldwBhFACHXxM6IFVwZGF0ZSBzdGF0dQCBKQYAgUMFADETCgoK&s=mscgen
diff --git a/graph/GuidelinesGraph.md b/graph/GuidelinesGraph.md
index f1894423..ea684fbf 100644
--- a/graph/GuidelinesGraph.md
+++ b/graph/GuidelinesGraph.md
@@ -10,11 +10,13 @@ Table of contents
- [Uniform Resource Locators (URLs)](#uniform-resource-locators-urls)
- [Resource modeling patterns](#resource-modeling-patterns)
- [Pros and cons](#pros-and-cons)
+ - [Nullable properties](#nullable-properties)
- [Query support](#query-support)
- [Behavior modeling](#behavior-modeling)
- [Error handling](#error-handling)
- - [Enums](#enums)
- - [API contract and non-backward compatible changes](#api-contract-and-non-backward-compatible-changes)
+ - [Limitations on core types](#limitations-on-core-types)
+ - [External standards](#external-standards)
+ - [API contract and nonbackward compatible changes](#api-contract-and-nonbackward-compatible-changes)
- [Versioning and deprecation](#versioning-and-deprecation)
- [Recommended API design patterns](#recommended-api-design-patterns)
- [References](#references)
@@ -25,7 +27,7 @@ Table of contents
When building a digital ecosystem API usability becomes a business priority. The success of your ecosystem depends on APIs that are easy to discover, simple to use, fit for purpose, and consistent across your products.
This document offers guidance that Microsoft Graph API producer teams MUST follow to
-ensure that Microsoft Graph has a consistent and easy-to-use API surface. A new API design should meet the following goals:
+ensure that Microsoft Graph has a consistent and easy-to-use API surface. A new API design SHOULD meet the following goals:
- Be developer friendly by using consistent naming, patterns, and web standards (HTTP, REST, JSON).
@@ -33,11 +35,9 @@ ensure that Microsoft Graph has a consistent and easy-to-use API surface. A new
- Be sustainable and evolvable by using clear API contracts.
-The Microsoft Graph REST API Guidelines are an extension of the
-[Microsoft REST API Guidelines](https://github.com/microsoft/api-guidelines/). It is assumed that readers are following the Microsoft REST API Guidelines except where this document outlines specific differences or exceptions to those guidelines. Together, these guidelines and a library of API patterns serve as the means by which API teams discuss and come to consensus on API review requirements.
+The Microsoft Graph REST API Guidelines consist of a concise overview document, a collection of articles on Graph standards, and a library of patterns that provide best practices for resolving common API design problems. Together, these documents serve as the means by which API teams discuss and come to consensus on API review requirements.
-Technology and software are constantly changing and evolving, and as such, this
-is intended to be a living document. API guidelines that change frequently lead to an uneven and inconsistent API surface. Consequently, this document will frequently change to add guidance in areas previously uncovered or to clarify existing guidance. It will less frequently change the directional guidance it has already provided. To suggest a change or propose a new idea,
+Technology and software are constantly changing and evolving, and as such, this document is intended to be a living document. API guidelines that change frequently lead to an uneven and inconsistent API surface.Therefore, the general principles and directions that this document offers will be more stable than the specific recommendations for areas that are new or significantly different. The guidance might change as needed to address new scenarios and to clarify existing guidance. The guidance might change as needed to address new scenarios and to clarify existing guidance. To suggest a change or propose a new idea,
[open an issue](https://github.com/microsoft/api-guidelines/issues/new/choose).
### Legend
@@ -56,7 +56,7 @@ If you do not follow this advice, you MUST disclose your reasons during the Micr
## Design approach
-The design of your API is arguably the most important investment you will make. API design is what creates the first impression for developers when they discover and learn how to use your APIs. We promote an API-first design approach where you begin your product design by focusing on how information is exchanged and represented and by creating an interface contract for your API, which is followed by design and implementation of the backing service. This approach ensures decoupling of the interface from your implementation and is essential for agility, predictability, and reuse of your APIs.
+The design of your API is arguably the most important investment you'll make. API design is what creates the first impression for developers when they discover and learn how to use your APIs. We promote an API-first design approach where you begin your product design by focusing on how information is exchanged and represented and by creating an interface contract for your API, which is followed by design and implementation of the backing service. This approach ensures decoupling of the interface from your implementation and is essential for agility, predictability, and reuse of your APIs.
An established interface contract allows developers to use your API while internal teams are still working on implementation; API specifications enable designing user experience and test cases in parallel. Starting with user-facing contracts also promotes a good understanding of system interactions, your modeling domain, and an understanding of how the service will evolve.
@@ -78,50 +78,59 @@ In general, API design includes the following steps:
1. Specify errors.
-When creating your API contract, you define resources based on the domain model supporting your service and identify interactions based on user scenarios. Good API design goes beyond modeling the current state of resources. It is important to plan ahead how the API evolves; to do this, it is essential to understand and document your user scenarios as the foundation of the API design. There is no one-to-one correspondence between domain model elements and API resources because you should simplify your customer facing APIs for better usability and to obfuscate implementation details.
+When creating your API contract, you define resources based on the domain model supporting your service and identify interactions based on user scenarios. Good API design goes beyond modeling the current state of resources. It's important to plan ahead how the API evolves; to do this, it's essential to understand and document your user scenarios as the foundation of the API design. There's no one-to-one correspondence between domain model elements and API resources because you SHOULD simplify your customer facing APIs for better usability and to obfuscate implementation details.
We recommend creating a simple resource diagram like the following to show resources and their relationships and make it easier to reason about modeling choices and the shape of your API.
-After you define your resources, it’s time to think about the behavior of your API, which can be expressed via HTTP methods and operational resources such as functions and actions. As you think about API behavior, you identify a happy path and various exceptions and deviations that will be expressed as errors and represented by using HTTP codes and error messages.
+After you define your resources, it’s time to think about the behavior of your API, which can be expressed via HTTP methods and operational resources such as functions and actions. As you think about API behavior, you identify a happy path and various exceptions and deviations that are expressed as errors and represented by using HTTP codes and error messages.
At every step of your design, you need to consider security, privacy, and compliance as intrinsic components of your API implementation.
### Naming
-API resources are typically described by nouns. Resource and property names appear in API URLs and payloads and must be descriptive and easy to understand. Ease of understanding comes from familiarity and recognition; therefore, when thinking about naming, you should favor consistency with other Microsoft Graph APIs, names in the product user interface, and industry standards. Microsoft Graph naming conventions follow the [Microsoft REST API naming guidelines](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#17-naming-guidelines).
+API resources are typically described by nouns. Resource and property names appear in API URLs and payloads and MUST be descriptive and easy to understand. Ease of understanding comes from familiarity and recognition; therefore, when thinking about naming, you SHOULD favor consistency with other Microsoft Graph APIs, names in the product user interface, and industry standards. Microsoft Graph naming conventions follow the [Naming guidelines](./articles/naming.md).
Following is a short summary of the most often used conventions.
| Requirements | Example |
| ------------------------------------------------------------------------|-------------------------------|
| :no_entry: **MUST NOT** use redundant words in names. | - **Right:** /places/{id}/**displayName** or /phones/{id}/**number** - **Wrong:** /places/{id}/**placeName** or /phones/{id}/**phoneNumber** |
-| :warning: **SHOULD NOT** use brand names in type or property names. | - **Right:** chat - **Wrong:** teamsChat |
+| :warning: **SHOULD NOT** use brand names in type or property names. | - **Right:** chat - **Wrong:** teamsChat - **NOTE:** there is an exception for resources that *only* exist under the `/admin` root segment and the `/users/{userId}/settings` path. |
| :warning: **SHOULD NOT** use acronyms or abbreviations unless they are broadly understood. | - **Right:** url or htmlSignature - **Wrong:** msodsUrl or dlp |
-| :heavy_check_mark: **MUST** use singular nouns for type names. | - **Right:** address - **Wrong:** addresses |
+| :heavy_check_mark: **MUST** use singular nouns for non-enum type names. | - **Right:** address - **Wrong:** addresses |
+| :heavy_check_mark: **MUST** use singular nouns for non-flags enum type names. | - **Right:** color - **Wrong:** colors |
+| :heavy_check_mark: **MUST** use plural nouns for flags enum type names. | - **Right:** diplayMethods - **Wrong:** displayMethod |
| :heavy_check_mark: **MUST** use plural nouns for collections (for listing type or collection properties). | - **Right:** addresses - **Wrong:** address |
| :ballot_box_with_check: **SHOULD** pluralize the noun even when followed by an adjective (a *postpositive*).| - **Right:** passersby or mothersInLaw - **Wrong:** notaryPublics or motherInLaws |
| **CASING** | |
| :heavy_check_mark: **MUST** use lower camel case for *all* names and namespaces. | - **Right:** automaticRepliesStatus - **Wrong:** kebab-case or snake_case |
-| :ballot_box_with_check: **SHOULD** case two-letter acronyms with the same case. | - **Right:** ioLimit or totalIOAmount - **Wrong:** iOLimit or totalIoAmount |
+| :ballot_box_with_check: **SHOULD** case two-letter acronyms with the same case. | - **Right:** ioLimit or totalIOAmount - **Right:** 'id' properties similar to driveId or applicationId - **Wrong:** iOLimit or totalIoAmount|
+| :ballot_box_with_check: **SHOULD** case `id` properties the same as a normal word. | - **Right:** id or fileId - **Wrong:** ID or fileID |
| :ballot_box_with_check: **SHOULD** case three+ letter acronyms the same as a normal word. | - **Right:** fidoKey or oauthUrl - **Wrong:** webHTML |
-| :no_entry: **MUST NOT** capitalize the word following a [prefix](https://www.thoughtco.com/common-prefixes-in-english-1692724) or words within a [compound word](http://www.learningdifferences.com/Main%20Page/Topics/Compound%20Word%20Lists/Compound_Word_%20Lists_complete.htm). | - **Right:** subcategory, geocoordinate, or crosswalk - **Wrong:** metaData, semiCircle, or airPlane |
+| :no_entry: **MUST NOT** capitalize the word following a [prefix](https://www.thoughtco.com/common-prefixes-in-english-1692724) or words within a [compound word](http://www.learningdifferences.com/Main%20Page/Topics/Compound%20Word%20Lists/Compound_Word_%20Lists_complete.htm). | - **Right:** subcategory, geo coordinate, or crosswalk - **Wrong:** metaData, semiCircle, or airPlane |
| :heavy_check_mark: **MUST** capitalize within hyphenated and open (spaced) compound words. | - **Right:** fiveYearOld, daughterInLaw, or postOffice - **Wrong:** paperclip or fullmoon |
| **PREFIXES AND SUFFIXES** | |
-| :heavy_check_mark: **MUST** suffix date and time properties with Date, Time, or DateTime | - **Right:** dueDate — an Edm.Date - **Right:** recurringMeetingTime — an Edm.TimeOfDay - **Right:** createdDateTime — an Edm.DateTimeOffset - **Wrong:** dueOn or startTime - **Right:** Instead, both of the preceding are an Edm.DateTimeOffset |
-| :ballot_box_with_check: **SHOULD** use the Duration type for durations, but if using an `int`, append the units. | - **Right:** passwordValidityPeriod — an Edm.Duration - **Right:** passwordValidityPeriodInDays — an Edm.Int32 (use of Edm.Duration type is preferable) - **Wrong:** passwordValidityPeriod — an Edm.Int32 |
+| :heavy_check_mark: **MUST** suffix date and time properties with Date, Time, or DateTime | - **Right:** dueDate—an Edm.Date - **Right:** recurringMeetingTime—an Edm.TimeOfDay - **Right:** createdDateTime—an Edm.DateTimeOffset - **Wrong:** dueOn or startTime - **Right:** Instead, both of the preceding are an Edm.DateTimeOffset |
+| :ballot_box_with_check: **SHOULD** use the Duration type for durations, but if using an `int`, append the units. | - **Right:** passwordValidityPeriod—an Edm.Duration - **Right:** passwordValidityPeriodInDays — an Edm.Int32 (use of Edm.Duration type is preferable) - **Wrong:** passwordValidityPeriod — an Edm.Int32 |
| :no_entry: **MUST NOT** use suffix property names with primitive type names unless the type is temporal. | - **Right:** isEnabled or amount - **Wrong:** enabledBool |
| :ballot_box_with_check: **SHOULD** prefix property names for properties concerning a different entity. | - **Right:** siteWebUrl on driveItem or userId on auditActor - **Wrong:** webUrl on contact when it's the companyWebUrl |
-| :ballot_box_with_check: **SHOULD** prefix Boolean properties with `is`, unless this leads to awkward or unnatural sounding names for Boolean properties. | - **Right:** isEnabled or isResourceAccount - **Wrong:** enabled or allowResourceAccount - **Right:** allowNewTimeProposals or allowInvitesFrom (subjectively more natural than the following examples) - **Wrong:** isNewTimeProposalsAllowed or isInvitesFromAllowed (subjectively more awkward that the preceding examples) |
+| :ballot_box_with_check: **SHOULD** prefix Boolean properties with `is`, unless this leads to awkward or unnatural sounding names for Boolean properties. | - **Right:** isEnabled or isResourceAccount - **Wrong:** enabled or allowResourceAccount - **Right:** hasChildren or hasSubscriptions - **Wrong:** isChildren or isSubscriptions - **Right:** allowNewTimeProposals or allowInvitesFrom (subjectively more natural than the following examples) - **Wrong:** isNewTimeProposalsAllowed or isInvitesFromAllowed (subjectively more awkward that the preceding examples) |
| :no_entry: **MUST NOT** use collection, response, or request suffixes. | - **Right:** addresses - **Wrong:** addressCollection |
-| :no_entry: **MUST NOT** contain product names. | - **Right:** chatMessages - **Wrong:** teamsMessages |
+
+#### Tree and graph structures
+
+When a tree or graph structure is being modeled, the direct sub-nodes are usually named `children` or `members`.
+If a property is desired that represents a "flattened" data structure, the property **SHOULD** be prefixed with "transitive", e.g. `transitiveChildren` or `transitiveMembers`.
+Such properties **MUST** represent a mathematically [transitive relationship](https://en.wikipedia.org/wiki/Transitive_relation).
+To simplify, if `A` is a child of `B` and `B` is a child of `C`, then `A` is a child of `C` via a transitive relationship; this **MUST** be true for properties using word "transitive" in their name.
### Uniform Resource Locators (URLs)
A Uniform Resource Locator (URL) is how developers access the resources of your API.
-Navigation paths to Microsoft Graph resources are generally broken into multiple segments,
+Navigation paths to Microsoft Graph resources are broken into multiple segments,
`{scheme}://{host}/{version}/{category}/[{pathSegment}][?{query}]` where:
- `scheme` and `host` segments are always [`https://graph.microsoft.com`](https://graph.microsoft.com/v1.0/users).
@@ -132,7 +141,7 @@ Navigation paths to Microsoft Graph resources are generally broken into multiple
- `pathSegment` is one or many navigation segments that can address an entity, collection of entities, property, or operation available for an entity.
-- `query` string must follow the OData standard for query representations and is covered in the Query section of OData specifications.
+- `query` string MUST follow the OData standard for query representations and is covered in the Query section of OData specifications.
While HTTP defines no constraints on how different resources are related, it does encourage the use of URL path segment hierarchies to convey relationships. In Microsoft Graph, relationships between resources are supported by the OData concepts of singletons, entity sets, entities, complex types, and navigation properties.
@@ -152,9 +161,9 @@ Effectively, top-level categories define a perimeter for the API surface; thus,
### Resource modeling patterns
-You can model structured resources for your APIs by using the OData entity type or complex type. The main difference between these types is that an entity type declares a key property to uniquely identify its objects, and a complex type does not. In Microsoft Graph, this key property is called `id` for server-created key values. If there is a natural name for the key property, then the workload can use that.
+You can model structured resources for your APIs by using the OData entity type or complex type. The main difference between these types is that an entity type declares a key property to uniquely identify its objects, and a complex type doesn't. In Microsoft Graph, this key property is called `id` for server-created key values. If there's a natural name for the key property, then the workload can use that.
-Because objects of complex types in Microsoft Graph don’t have unique identifiers, they are not directly addressable via URIs. Therefore, you must use entity types to model addressable resources such as individually addressable items within a collection. For more information, see the [Microsoft REST API Guidelines collection URL patterns](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#93-collection-url-patterns). Complex types are better suited to represent composite properties of API entities.
+Because objects of complex types in Microsoft Graph don’t have unique identifiers, they are not directly addressable via URIs. Therefore, you SHOULD use entity types to model addressable resources such as individually addressable items within a collection. For more information, see the [Collection guidance](./articles/collections.md). Complex types are better suited to represent composite properties of API entities.
```xml
@@ -213,11 +222,11 @@ Following are a few pros and cons to decide which pattern to use:
- **hierarchy** and **facets** (to a slightly lesser degree) are well-suited for strongly typed client programming languages, whereas **flat bag** is more familiar to developers of less strongly typed languages.
-- **facets** has the potential to model what is typically associated with multiple inheritance.
+- **facets** has the potential to model what is typically associated with multiple inheritances.
- **facets** and **flat bag** lend to syntactically simpler filter query expression. **hierarchy** is more explicit but requires the cast segments in the filter query.
-- **hierarchy** can be refined by annotating the collections with OData derived type constraints; see [validation vocabulary](https://github.com/oasis-tcs/odata-vocabularies/blob/main/vocabularies/Org.OData.Validation.V1.md). This annotation restricts the values to certain sub-trees of an inheritance **hierarchy**. It makes it very explicit that the collection only contains elements of some of the subtypes and helps to not return objects of a type that are semantically not suitable.
+- **hierarchy** can be refined by annotating the collections with OData derived type constraints; see [validation vocabulary](https://github.com/oasis-tcs/odata-vocabularies/blob/main/vocabularies/Org.OData.Validation.V1.md). This annotation restricts the values to certain sub-trees of an inheritance **hierarchy**. It makes it explicit that the collection only contains elements of some of the subtypes and helps to not return objects of a type that are semantically not suitable.
> **Note:**
> As can be seen in a few of the pros and cons, one of the important aspects discussed here is that the API design goes beyond the syntactical aspects of the API. Therefore, it is important to plan ahead how the API evolves, lay the foundation, and allow users to form a good understanding of the semantics of the API. **Changing the semantics is always a breaking change.** The different modeling patterns differ in how they express syntax and semantics and how they allow the API to evolve without breaking compatibility. For more information, see [API contract and non-backward compatible changes](#api-contract-and-non-backward-compatible-changes) later in this article.
@@ -226,11 +235,11 @@ Following are a few pros and cons to decide which pattern to use:
The facet and flat bag approaches often require nullable properties, so it is important to still use non-nullable properties where appropriate.
Since inheritance can often remove the use of nullable properties completely, it is also important to know when nullable properties are necessary.
-See [Nullable properties](./nullable.md) for more details.
+See [Nullable properties](./articles/nullable.md) for more details.
### Query support
-Microsoft Graph APIs should support basic query options in conformance with OData specifications and [Microsoft REST API Guidelines for error condition responses](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#7102-error-condition-responses).
+Microsoft Graph APIs returning collections of resources SHOULD support basic query options in conformance with [OData specifications](http://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#sec_PassingQueryOptionsintheRequestBody) and [Collection guidance](./articles/collections.md).
|Requirements |
|----------------------------------------------------------------------------------------------------|
@@ -238,23 +247,23 @@ Microsoft Graph APIs should support basic query options in conformance with ODat
| :ballot_box_with_check: **SHOULD** support `/entityTypeCollection/{id}?$expand=navProp1` option for navigation properties of entities. |
| :ballot_box_with_check: **SHOULD** support `$filter` with `eq` and `ne` operations on properties of entity collections. |
| :heavy_check_mark: **MUST** support pagination of collections (of entity types or complex types) using a [nextLink](http://docs.oasis-open.org/odata/odata-json-format/v4.01/odata-json-format-v4.01.html#sec_ControlInformationnextLinkodatanextL). |
-| :ballot_box_with_check: **MAY** support [server-driven pagination](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#981-server-driven-paging) of collections using `$skiptoken`. |
-| :ballot_box_with_check: **SHOULD** support [client-driven pagination](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#982-client-driven-paging) of collections using `$top` and `$skip`. |
+| :ballot_box_with_check: **MAY** support [server-driven pagination](./articles/collections.md#81-server-driven-paging) of collections using `$skiptoken`. |
+| :ballot_box_with_check: **SHOULD** support [client-driven pagination](./articles/collections.md#82-client-driven-paging) of collections using `$top` and `$skip`. |
| :ballot_box_with_check: **SHOULD** support `$count` for collections. |
| :ballot_box_with_check: **SHOULD** support sorting with `$orderby` both ascending and descending on properties of the entities. |
-The query options part of an OData URL can be quite long, potentially exceeding the maximum length of URLs supported by components involved in transmitting or processing the request. One way to avoid this is to use the POST verb instead of GET with the `$query` segment, and pass the query options part of the URL in the request body as described in the chapter
+The query options part of an OData URL can be long, potentially exceeding the maximum length of URLs supported by components involved in transmitting or processing the request. One way to avoid this is to use the POST verb instead of GET with the `$query` segment, and pass the query options part of the URL in the request body as described in the chapter
[OData Query Options](http://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#sec_PassingQueryOptionsintheRequestBody).
Another way to avoid this is to use JSON batch as described in the [Microsoft Graph batching documentation](https://docs.microsoft.com/graph/json-batching#bypassing-url-length-limitations-with-batching).
### Behavior modeling
-The HTTP operations dictate how your API behaves. The URL of an API, along with its request/response bodies, establishes the overall contract that developers have with your service. As an API provider, how you manage the overall request/response pattern should be one of the first implementation decisions you make.
+The HTTP operations dictate how your API behaves. The URL of an API, along with its request/response bodies, establishes the overall contract that developers have with your service. As an API provider, how you manage the overall request/response pattern SHOULD be one of the first implementation decisions you make.
-If possible, APIs SHOULD use resource-based designs with standard HTTP methods rather than operation resources. Operation resources are either functions or actions. According to [OData standards](http://docs.oasis-open.org/odata/odata/v4.0/errata03/os/complete/part3-csdl/odata-v4.0-errata03-os-part3-csdl-complete.html#_The_edm:Function_Element_2), a function represents an operation that returns a single instance or collection of instances of any type and doesn’t have an observable side effect. An action might have side effects and might return a result represented as a single entity or collection of any type.
+If possible, APIs SHOULD use resource-based designs with standard HTTP methods rather than operation resources. Operation resources are either functions or actions. According to [OData standards](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#_Toc31359009), a function represents an operation that returns a single instance or collection of instances of any type and doesn’t have an observable side effect. An action might have side effects and might return a result represented as a single entity or collection of any type.
-| Microsoft Graph rules for modeling behavior |
+| Microsoft Graph rules for behavior modeling |
|------------------------------------------------------------------|
| :heavy_check_mark: **MUST** use POST to create new entities in insertable entity sets or collections. This approach requires the service to produce a system-generated key, or for a caller to provide a key in the request payload. |
| :ballot_box_with_check: **SHOULD** additionally use PATCH to create new entities in insertable entity sets or collections. This [Upsert](./patterns/upsert.md) approach requires the caller to provide a key in the request URL. |
@@ -264,14 +273,13 @@ If possible, APIs SHOULD use resource-based designs with standard HTTP methods r
| :warning: **SHOULD NOT** use PUT for updating resources. |
| :ballot_box_with_check: **SHOULD** avoid using multiple round trips to complete a single logical operation. |
-Operation resources must have a binding parameter that matches the type of the bound resource. In addition, both actions and functions support overloading, meaning an API definition might contain multiple actions or functions with the same name.
-
-For a complete list of standard HTTP operations, see the [Microsoft REST API Guidelines error condition responses](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#7102-error-condition-responses).
+Operation resources MUST have a binding parameter that matches the type of the bound resource. In addition, both actions and functions support overloading, meaning an API definition might contain multiple actions or functions with the same name.
+For an additional list of standard HTTP methods, see the [RFC7230](https://www.rfc-editor.org/rfc/rfc9112)).
### Error handling
-Microsoft REST API Guidelines provide guidelines that Microsoft Graph APIs should follow when returning error condition responses. You can improve API traceability and consistency by using the recommended Microsoft Graph error model and the Microsoft Graph utilities library to provide a standard implementation for your service:
+ To improve API traceability and consistency you MUST use the recommended Microsoft Graph error model and the Microsoft Graph utilities library to provide a standard implementation for your service. The value for the "message" name/value pair MUST be a human-readable representation of the error, tailored to provide enough information for the developer to understand the error and take appropriate action. The message is intended only as an aid to developers and should not be exposed to end users.
```http
{
@@ -279,15 +287,13 @@ Microsoft REST API Guidelines provide guidelines that Microsoft Graph APIs shoul
"code": "badRequest",
"message": "Cannot process the request because a required field is missing.",
"target": "query",
- "innererror": {
- "code": "requiredFieldMissing",
-
- }
- }
+ "innererror":{
+ "code": "requiredFieldMissing"
+ }
}
```
-The top-level error code must match the HTTP response status code description, converted to camelCase, as listed in the [Status Code Registry (iana.org)](https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml). The following examples demonstrate error modeling for common use cases:
+The top-level error code MUST match the HTTP response status code description, converted to camelCase, as listed in the [Status Code Registry (iana.org)](https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml). The following examples demonstrate error modeling for common use cases:
- **Simple error**: An API wants to report an error with top-level details only. The error object contains the top-level error code, message and target (optional).
@@ -296,7 +302,7 @@ The top-level error code must match the HTTP response status code description, c
"error": {
"code": "badRequest",
"message": "Cannot process the request because it is malformed or incorrect.",
- "target": "resource X (Optional)"
+ "target": "resource"
}
}
```
@@ -307,10 +313,9 @@ The top-level error code must match the HTTP response status code description, c
{
"error": {
"code": "badRequest",
- "message": "Cannot process the request because it is malformed or incorrect.",
+ "message": "Cannot process the request because a required field is missing.",
"innererror": {
- "code": "requiredFieldOrParameterMissing",
-
+ "code": "requiredFieldOrParameterMissing"
}
}
}
@@ -323,19 +328,43 @@ The top-level error code must match the HTTP response status code description, c
| :heavy_check_mark: **MUST** return a 429 Too Many Requests error when the client exceeded throttling limits, and a 503 Service Unavailable error when the service overloaded but the client is within throttling limits.|
| :ballot_box_with_check: **SHOULD** return a 404 Not Found error if a 403 error would result in information disclosure. |
+For more detailed guidance, see the article on [Error condition responses](./articles/errorResponses.md).
+
For a complete mapping of error codes to HTTP statuses, see
[rfc7231 (ietf.org)](https://datatracker.ietf.org/doc/html/rfc7231#section-6).
-## API contract and non-backward compatible changes
+### Limitations on core types
+
+The types `user`, `group`, and `device` should not have any new structural property(s) added, without compelling justification.
+Instead, model the concept represented in those property(s) as a new entity and do one of the following:
+1. Add navigation from `user`, `group`, or `device` to the new entity.
+2. Add a navigation from the new entity to `user`, `group` or `device`.
+
+More details and examples are available in [Core types](./articles/coreTypes.md).
-The Microsoft Graph definition of breaking changes is based on the
-[Microsoft REST API Guidelines definition of a breaking change](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#123-definition-of-a-breaking-change). In general, making all but additive changes to the API contract for existing elements is considered breaking. Adding new elements is allowed and is not considered a breaking change.
+## External standards
+
+For ease of client use and interoperatibility, some APIs might implement a standard that is defined external to Microsoft Graph and OData.
+Workloads SHOULD follow these standards exactly, even if they conflict with the OData standard and/or the Microsoft Graph guidelines.
+Workloads SHOULD define these standards in their CSDL model if they do not conflict with the OData standard.
+Standards that *do* conflict with the OData standard might be defined in the CSDL in one of two ways:
+1. Using `Edm.Untyped` only and support for the external standard will come directly from the service implementation; OR
+2. Adding CSDL elements to model the external standard using `Edm.String` for `EnumType`s that conflict with the OData standard and `Edm.Untyped` wherever any other conflict with the OData standard occurs.
+
+In either case, any use of `Edm.String` instead of an `EnumType` or any use of `Edm.Untyped` MUST provide a [description annotation](https://github.com/oasis-tcs/odata-vocabularies/blob/main/vocabularies/Org.OData.Core.V1.xml#L105) to document references to the standard that the client is expected to follow.
+The benefit of the second approach is that strongly-typed models have SDK support for clients and also have significant tooling support for both the workload and clients.
+Note that it's backwards compatible for a workload to migrate from the second approach to the first approach in case the external standard is *initially* compliant with the OData standard and *later* conflicts with the OData standard.
+
+## API contract and nonbackward compatible changes
+
+The Microsoft Graph defines breaking changes as any change that requires a client to change its implementation to continue working with the service, it includes changes to the API contract, API behavior, and nonbackward compatible changes.
+In general, making all but additive changes to the API contract for existing elements is considered breaking. Adding new elements is allowed and is not considered a breaking change.
**Non-breaking changes:**
-- Adding properties that are nullable or have a default value
+- To add properties that are nullable or have a default value
- Adding a member after the sentinel member to an evolvable enumeration
- Removing, renaming, or changing the type of annotation
- Changing the order of properties
@@ -348,7 +377,7 @@ The Microsoft Graph definition of breaking changes is based on the
- Removing, renaming, or changing an incompatible type of a declared property
- Removing or renaming APIs or API parameters
- Adding a required request header
-- Adding EnumType members for non-evolvable enumerations
+- Adding EnumType members for nonevolvable enumerations
- Adding Nullable="false" properties to existing types
- Adding a parameter not marked as [Nullable](http://docs.oasis-open.org/odata/odata-csdl-xml/v4.01/odata-csdl-xml-v4.01.html#sec_Nullable) to existing actions
- Adding a parameter not marked as [Optional](https://github.com/oasis-tcs/odata-vocabularies/blob/main/vocabularies/Org.OData.Core.V1.md#OptionalParameter) to an existing function
@@ -356,11 +385,13 @@ The Microsoft Graph definition of breaking changes is based on the
- Introducing server-side pagination to existing collections
- Making significant changes to the performance of APIs such as increased latency, rate limits, or concurrency
+The applicable changes described in the [Model Versioning of the OData V4.01 spec](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#sec_ModelVersioning) SHOULD be considered part of the minimum bar that all services MUST consider a breaking change.
+
### Versioning and deprecation
-As the market and technology evolves, your APIs will require modifications. In this case, you must avoid breaking changes and add new resources and features incrementally. If that is not possible, then you must version elements of your APIs. Microsoft Graph allows versioning of elements, including entities and properties. Versioning involves adding a new, uniquely named version of the element and marking the old version as deprecated.
+As the market and technology evolves, your APIs will require modifications. In this case, you MUST avoid breaking changes and add new resources and features incrementally. If that isn't possible, then you MUST version elements of your APIs. Microsoft Graph allows versioning of elements, including entities and properties. Versioning involves adding a new, uniquely named version of the element and marking the old version as deprecated.
-In some cases, there is a natural new name for the element. In other cases, where the original name is still the most descriptive, the suffix _v2 can be added to the original name to make it unique. The original element is then marked as deprecated by using annotations.
+In some cases, there's a natural new name for the element. In other cases, where the original name is still the most descriptive, the suffix _v2 can be added to the original name to make it unique. The original element is then marked as deprecated by using annotations.
Microsoft Graph provides two public endpoints to support the API lifecycle:
- [API sets on the v1.0 endpoint](https://graph.microsoft.com/v1.0) are in general availability (GA) status.
@@ -370,17 +401,18 @@ Microsoft Graph APIs in the GA version guarantee API stability and consistency f
On the beta endpoint, breaking changes and deprecation of APIs are allowed with consideration of dependencies and customer impact. It is a best practice to test new element versions on the beta endpoint at first and then promote API changes to the GA endpoint.
-Detailed requirements for versioning and deprecation are described in the [Deprecation guidelines](./deprecation.md).
+Detailed requirements for versioning and deprecation are described in the [Deprecation guidelines](./articles/deprecation.md).
## Recommended API design patterns
-The guidelines in previous sections are intentionally brief and provide a jump start for Microsoft Graph API developers. More detailed design guidance about REST APIs is published at the [Microsoft REST API Guidelines](https://github.com/microsoft/api-guidelines/). Microsoft Graph-specific patterns are outlined in the following table.
+The guidelines in previous sections provide a brief overview and a quick start for Microsoft Graph API developers. For a more detailed dive into a specific topic, you can explore [additional articles](./articles/) or learn more about [modeling patterns with the Microsoft Graph](./patterns/) listed in the following table.
| Pattern | Description |
|--------------------------------------------------|----------------------------------------------------------------------------|
| [Alternate key](./patterns/alternate-key.md) | Uniquely identify and query resources using an alternate key. |
| [Change tracking](./patterns/change-tracking.md) | Keep API consumers in sync with changes without polling. |
| [Collection subsets](./patterns/subsets.md) | Model collection subsets |
+| [Default properties](./patterns/default-properties.md) | Omit non-default properties from the response unless they are explicitly requested using `$select`.
| [Dictionary](./patterns/dictionary.md) | Clients can provide an unknown quantity of data elements of the same type. |
| [Evolvable enums](./patterns/evolvable-enums.md) | Extend enumerated types without breaking changes. |
| [Facets](./patterns/facets.md) | Model parent-child relationships. |
@@ -396,8 +428,8 @@ The guidelines in previous sections are intentionally brief and provide a jump s
## References
-- [Microsoft REST API Guidelines](https://github.com/microsoft/api-guidelines/)
-- [OData guidelines](http://www.odata.org/documentation/)
-- [RESTful web API design](https://docs.microsoft.com/azure/architecture/best-practices/api-design)
- [Microsoft Graph documentation](https://docs.microsoft.com/graph/overview)
+- [Microsoft REST API Guidelines-deprecated](Guidelines-deprecated.md)
+- [OData guidelines](http://www.odata.org/documentation/)
+- [Azure RESTful web API design](https://docs.microsoft.com/azure/architecture/best-practices/api-design)
- [Graph Explorer](https://developer.microsoft.com/graph/graph-explorer)
diff --git a/graph/articles/collections.md b/graph/articles/collections.md
new file mode 100644
index 00000000..6a24d9f0
--- /dev/null
+++ b/graph/articles/collections.md
@@ -0,0 +1,318 @@
+# Collections
+
+## 1. Item keys
+
+Services SHOULD support durable identifiers for each item in the collection, and that identifier SHOULD be represented in JSON as "id". These durable identifiers are often used as item keys.
+
+Collections MAY support delta queries, see the [Change Tracking pattern](../patterns/change-tracking.md) section for more details.
+
+## 2. Serialization
+
+Collections are represented in JSON using standard array notation for `value` property.
+
+## 3. Collection URL patterns
+
+While there are multiple collections located directly under the Graph root going forward, you MUST have a singleton for the top-level segment and scope collections to an appropriate singleton. Collection names SHOULD be plural nouns when possible. Collection names shouldn't use suffixes, such as "Collection" or "List".
+
+For example:
+
+```http
+GET https://graph.microsoft.com/v1.0/teamwork/devices
+```
+
+Collections elements MUST be addressable by a unique id property. The id property MUST be a String and MUST be unique within the collection. The id property MUST be represented in JSON as "id".
+For example:
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices/0f3ce432-e432-0f3c-32e4-3c0f32e43c0f
+```
+
+Where:
+
+- "https://graph.microsoft.com/beta/teamwork" - the service root represented as the combination of host (site URL) + the root path to the service.
+- "devices" – the name of the collection, unabbreviated, pluralized.
+- "0f3ce432-e432-0f3c-32e4-3c0f32e43c0f" – the value of the unique id property that MUST be the raw string/number/guid value with no quoting but properly escaped to fit in a URL segment.
+
+### 3.1. Nested collections and properties
+
+Collection items MAY contain other collections.
+For example, a devices collection MAY contain device resources that have multiple mac addresses:
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices/0f3ce432-e432-0f3c-32e4-3c0f32e43c0f
+```
+
+```json
+
+{
+ "value": {
+ "@odata.type": "#microsoft.graph.teamworkDevice",
+ "id": "0f3ce432-e432-0f3c-32e4-3c0f32e43c0f",
+ "deviceType": "CollaborationBar",
+ "hardwareDetail": {
+ "serialNumber": "0189",
+ "uniqueId": "5abcdefgh",
+ "macAddresses": [],
+ "manufacturer": "yealink",
+ "model": "vc210"
+ },
+ ...
+ }
+}
+```
+
+## 4. Big collections
+
+As data grows, so do collections.
+Services SHOULD support server-side pagination from day one even for all collections, as adding pagination is a breaking change.
+When multiple pages are available, the serialization payload MUST contain the opaque URL for the next page as appropriate.
+Refer to the [paging guidance](../Guidelines-deprecated.md#98-pagination) for more details.
+
+Clients MUST be resilient to collection data being either paged or nonpaged for any given request.
+
+```json
+{
+ "value":[
+ { "id": "Item 1","price": 9 95,"sizes": null},
+ { … },
+ { … },
+ { "id": "Item 99","price": 5 99,"sizes": null}
+ ],
+ "@nextLink": "{opaqueUrl}"
+}
+```
+
+## 5. Changing collections
+
+POST requests are not idempotent.
+This means that two POST requests sent to a collection resource with exactly the same payload MAY lead to multiple items being created in that collection.
+This is often the case for insert operations on items with a server-side generated id.
+For additional information refer to [Upsert pattern](../patterns/upsert.md).
+
+For example, the following request:
+
+```http
+POST https://graph.microsoft.com/beta/teamwork/devices
+```
+
+Would lead to a response indicating the location of the new collection item:
+
+```http
+201 Created
+Location: https://graph.microsoft.com/beta/teamwork/devices/123
+```
+
+And once executed again, would likely lead to another resource:
+
+```http
+201 Created
+Location: https://graph.microsoft.com/beta/teamwork/devices/124
+```
+
+## 6. Sorting collections
+
+The results of a collection query MAY be sorted based on property values.
+The property is determined by the value of the _$orderBy_ query parameter.
+
+The value of the _$orderBy_ parameter contains a comma-separated list of expressions used to sort the items.
+A special case of such an expression is a property path terminating on a primitive property.
+
+The expression MAY include the suffix "asc" for ascending or "desc" for descending, separated from the property name by one or more spaces.
+If "asc" or "desc" is not specified, the service MUST order by the specified property in ascending order.
+
+NULL values MUST sort as "less than" non-NULL values.
+
+Items MUST be sorted by the result values of the first expression, and then items with the same value for the first expression are sorted by the result value of the second expression, and so on.
+The sort order is the inherent order for the type of the property.
+
+For example:
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices?$orderBy=companyAssetTag
+```
+
+Will return all devices sorted by companyAssetTag in ascending order.
+
+For example:
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices?$orderBy=companyAssetTag desc
+```
+
+Will return all devices sorted by companyAssetTag in descending order.
+
+Sub-sorts can be specified by a comma-separated list of property names with OPTIONAL direction qualifier.
+
+For example:
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices?$orderBy=companyAssetTag desc,activityState
+```
+
+Will return all devices sorted by companyAssetTag in descending order and a secondary sort order of activityState in ascending order.
+
+Sorting MUST compose with filtering see [Odata 4.01 spec](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#_Toc31361038) for more details.
+
+### 6.1. Interpreting a sorting expression
+
+Sorting parameters MUST be consistent across pages, as both client and server-side paging is fully compatible with sorting.
+
+If a service does not support sorting by a property named in a _$orderBy_ expression, the service MUST respond with an error message as defined in the Responding to Unsupported Requests section.
+
+## 7. Filtering
+
+The _$filter_ querystring parameter allows clients to filter a collection of resources that are addressed by a request URL.
+The expression specified with _$filter_ is evaluated for each resource in the collection, and only items where the expression evaluates to true are included in the response.
+Resources for which the expression evaluates to false or to null, or which reference properties that are unavailable due to permissions, are omitted from the response.
+
+Example: return all devices with activity state equal to 'Active'
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices?$filter=(activityState eq 'Active')
+```
+
+The value of the _$filter_ option is a Boolean expression.
+
+### 7.1. Filter operations
+
+Services that support _$filter_ SHOULD support the following minimal set of operations.
+
+Operator | Description | Example
+-------------------- | --------------------- | -----------------------------------------------------
+Comparison Operators | |
+eq | Equal | city eq 'Redmond'
+ne | Not equal | city ne 'London'
+gt | Greater than | price gt 20
+ge | Greater than or equal | price ge 10
+lt | Less than | price lt 20
+le | Less than or equal | price le 100
+Logical Operators | |
+and | Logical and | price le 200 and price gt 3.5
+or | Logical or | price le 3.5 or price gt 200
+not | Logical negation | not price le 3.5
+Grouping Operators | |
+( ) | Precedence grouping | (priority eq 1 or city eq 'Redmond') and price gt 100
+
+Services MUST use the following operator precedence for supported operators when evaluating _$filter_ expressions.
+Operators are listed by category in order of precedence from highest to lowest.
+Operators in the same category have equal precedence:
+
+| Group | Operator | Description |
+|:----------------|:---------|:----------------------|
+| Grouping | ( ) | Precedence grouping |
+| Unary | not | Logical Negation |
+| Relational | gt | Greater Than |
+| | ge | Greater Than or Equal |
+| | lt | Less Than |
+| | le | Less Than or Equal |
+| Equality | eq | Equal |
+| | ne | Not Equal |
+| Conditional AND | and | Logical And |
+| Conditional OR | or | Logical Or |
+
+## 8. Pagination
+
+RESTful APIs that return collections MAY return partial sets.
+Consumers of these services MUST expect partial result sets and correctly page through to retrieve an entire set.
+
+There are two forms of pagination that MAY be supported by RESTful APIs.
+Server-driven paging allows servers to even out load across clients and mitigates against denial-of-service attacks by forcibly paginating a request over multiple response payloads.
+Client-driven paging enables clients to request only the number of resources that it can use at a given time.
+
+Sorting and Filtering parameters MUST be consistent across pages, because both client- and server-side paging is fully compatible with both filtering and sorting.
+
+### 8.1. Server-driven paging
+
+Paginated responses MUST indicate a partial result by including a `@odata.nextLink` token in the response.
+The absence of a `nextLink` token means that no additional pages are available, see [Odata 4.01 spec](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#sec_ServerDrivenPaging) for more details.
+
+Clients MUST treat the `nextLink` URL as opaque, which means that query options may not be changed while iterating over a set of partial results.
+
+Example:
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ "value": [...],
+ "@odata.nextLink": "{opaqueUrl}"
+}
+```
+
+### 8.2. Client-driven paging
+
+Clients MAY use _$top_ and _$skip_ query parameters to specify a number of results to return and an offset into the collection.
+
+The server SHOULD honor the values specified by the client; however, clients MUST be prepared to handle responses that contain a different page size or contain a `@odata.nextLink` token.
+
+When both _$top_ and _$skip_ are given by a client, the server SHOULD first apply _$skip_ and then _$top_ on the collection.
+
+Note: If the server can't honor _$top_ and/or _$skip_, the server MUST return an error to the client informing about it instead of just ignoring the query options.
+This will avoid the risk of the client making assumptions about the data returned.
+
+Example:
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices?$top=5&$skip=2
+
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ "value": [...]
+}
+```
+
+### 8.3. Additional considerations
+
+**Stable order prerequisite:** Both forms of paging depend on the collection of items having a stable order.
+The server MUST supplement any specified order criteria with additional sorts (typically by key) to ensure that items are always ordered consistently.
+
+**Missing/repeated results:** Even if the server enforces a consistent sort order, results MAY be missing or repeated based on creation or deletion of other resources.
+Clients MUST be prepared to deal with these discrepancies.
+The server SHOULD always encode the record ID of the last read record, helping the client in the process of managing repeated/missing results.
+
+**Combining client- and server-driven paging:** Note that client-driven paging does not preclude server-driven paging.
+If the page size requested by the client is larger than the default page size supported by the server, the expected response would be the number of results specified by the client, paginated as specified by the server paging settings.
+
+**Page Size:** Clients MAY request server-driven paging with a specific page size by specifying a _$maxpagesize_ preference.
+The server SHOULD honor this preference if the specified page size is smaller than the server's default page size.
+
+**Paginating embedded collections:** It is possible for both client-driven paging and server-driven paging to be applied to embedded collections.
+If a server paginates an embedded collection, it MUST include additional `nextLink` tokens as appropriate.
+
+**Recordset count:** Developers who want to know the full number of records across all pages, MAY include the query parameter _$count=true_ to tell the server to include the count of items in the response.
+
+## 9. Compound collection operations
+
+Filtering, Sorting and Pagination operations MAY all be performed against a given collection.
+When these operations are performed together, the evaluation order MUST be:
+
+1. **Filtering**. This includes all range expressions performed as an AND operation.
+2. **Sorting**. The potentially filtered list is sorted according to the sort criteria.
+3. **Pagination**. The materialized paginated view is presented over the filtered, sorted list. This applies to both server-driven pagination and client-driven pagination.
+
+## 10. Empty Results
+
+When a filter is performed on a collection and the result set is empty you MUST respond with a valid response body and a 200 response code.
+In this example the filters supplied by the client resulted in a empty result set.
+The response body is returned as normal and the _value_ attribute is set to a empty collection.
+You SHOULD maintain consistency in your API whenever possible.
+
+```http
+GET https://graph.microsoft.com/beta/teamwork/devices?$filter=('deviceType' eq 'Collab' or companyAssetTa eq 'Tag1')
+Accept: application/json
+
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{
+ "value": []
+}
+```
diff --git a/graph/articles/coreTypes.md b/graph/articles/coreTypes.md
new file mode 100644
index 00000000..9484ea5c
--- /dev/null
+++ b/graph/articles/coreTypes.md
@@ -0,0 +1,94 @@
+# Core Types
+
+## Overview
+
+Types exist in Microsoft Graph which are highly-connected/central to the Microsoft Graph ecosystem. Often, these types are in the position of being able to contain structural properties relevant to other APIs, because they are connected to many entities in Microsoft Graph.
+
+Structural properties should be only added to these core types when they are intrinsic to the entity itself, and strictly not for the purpose of convenience due to the entity's position in Microsoft Graph.
+
+## Core Types in Microsoft Graph
+
+The following types are identified as core types, and will require strong justification to allow new structural properties to be added in all cases.
+
+- ```user```
+- ```group```
+- ```device```
+
+## Alternatives to Adding Structural Properties
+
+Instead of adding a structural property to the existing core type (`user`, `group` or `device`), create a new type that models the information captured in the proposed structural property(s).
+Then, model the relationship between the existing core type and the new type by adding a navigation property. For information on modeling with navigation properties, see [Navigation Property](../patterns/navigation-property.md).
+
+## Example:
+
+Modeling adding "bank account information", which includes two properties `accountNumber` and `routingNumber`, to entity type ```user```.
+
+### Don't:
+
+Don't add new properties to core types such as `user`.
+
+```xml
+
+
+
+
+```
+
+### Do:
+
+Model the information by creating a new type and model the relationship to the existing core type with a navigation property. To determine which option is most appropriate, see [Navigation Property](../patterns/navigation-property.md):
+
+#### Option 1: Add a navigation property on the existing core type to the new type, containing the new type.
+
+Define the new entity type:
+```xml
+
+
+
+
+```
+
+Add a contained navigation from user to the new entity type:
+```xml
+
+
+
+```
+
+#### Option 2: Contain the new type in an entity set elsewhere, and add a navigation property to the new type on the existing core type.
+
+Define the new entity type:
+```xml
+
+
+
+
+```
+
+Contain the new entity type in an entity set or singleton:
+```xml
+
+```
+
+Add a navigation from user to the new type:
+```xml
+
+
+
+```
+
+#### Option 3: Contain the new type in an entity set elsewhere, and add a navigation property to the existing core type on the new type.
+
+Define the new entity type, with a navigation to the user:
+```xml
+
+
+
+
+
+```
+
+Contain the new entity type in an entity set or singleton:
+```xml
+
+```
diff --git a/graph/deprecation.md b/graph/articles/deprecation.md
similarity index 100%
rename from graph/deprecation.md
rename to graph/articles/deprecation.md
diff --git a/graph/articles/errorResponses.md b/graph/articles/errorResponses.md
new file mode 100644
index 00000000..ea573925
--- /dev/null
+++ b/graph/articles/errorResponses.md
@@ -0,0 +1,133 @@
+# Error condition responses
+
+For non-success conditions, developers SHOULD be able to write one piece of code that handles errors consistently across different Microsoft REST API services.
+This allows building of simple and reliable infrastructure to handle exceptions as a separate flow from successful responses.
+The following is based on the OData v4 JSON spec.
+However, it is very generic and does not require specific OData constructs.
+APIs SHOULD use this format even if they are not using other OData constructs.
+
+The error response MUST be a single JSON object.
+This object MUST have a name/value pair named "error". The value MUST be a JSON object.
+
+This object MUST contain name/value pairs with the names "code" and "message", and it MAY contain name/value pairs with the names "target", "details" and "innererror."
+
+The value for the "code" name/value pair is a language-independent string and MUST match the HTTP response status code description, converted to camelCase, as listed in the [Status Code Registry (iana.org)](https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml)
+For example, if the HTTP status code is "Not Found", then the "code" value MUST be "notFound".
+
+Most services will require a larger number of more specific error codes, which are not interesting to all clients.
+These error codes SHOULD be exposed in the "innererror" name/value pair as described below.
+Introducing a new value for "code" that is visible to existing clients is a breaking change and requires a version increase.
+Services can avoid breaking changes by adding new error codes to "innererror" instead.
+
+The value for the "message" name/value pair MUST be a human-readable representation of the error.
+It is intended as an aid to developers and is not suitable for exposure to end users.
+Services wanting to expose a suitable message for end users MUST do so through an [odata-json-annotations](https://docs.oasis-open.org/odata/odata-json-format/v4.01/cs02/odata-json-format-v4.01-cs02.html#sec_AnnotateaJSONObject) or custom property.
+Services SHOULD NOT localize "message" for the end user, because doing so might make the value unreadable to the app developer who may be logging the value, as well as make the value less searchable on the Internet.
+
+The value for the "target" name/value pair is the target of the particular error (e.g., the name of the property in error).
+
+The value for the "details" name/value pair MUST be an array of JSON objects that MUST contain name/value pairs for "code" and "message", and MAY contain a name/value pair for "target", as described above.
+The objects in the "details" array usually represent distinct, related errors that occurred during the request.
+See example below.
+
+The value for the "innererror" name/value pair MUST be an object.
+The contents of this object are service-defined.
+Services wanting to return more specific errors than the root-level code MUST do so by including a name/value pair for "code" and a nested "innererror". Each nested "innererror" object represents a higher level of detail than its parent.
+When evaluating errors, clients MUST traverse through all of the nested "innererrors" and choose the deepest one that they understand.
+This scheme allows services to introduce new error codes anywhere in the hierarchy without breaking backwards compatibility, so long as old error codes still appear.
+The service MAY return different levels of depth and detail to different callers.
+For example, in development environments, the deepest "innererror" MAY contain internal information that can help debug the service.
+To guard against potential security concerns around information disclosure, services SHOULD take care not to expose too much detail unintentionally.
+Error objects MAY also include custom server-defined name/value pairs that MAY be specific to the code.
+Error types with custom server-defined properties SHOULD be declared in the service's metadata document.
+See example below.
+
+Error responses MAY contain Odata JSON annotations in any of their JSON objects.
+
+We recommend that for any transient errors that may be retried, services SHOULD include a Retry-After HTTP header indicating the minimum number of seconds that clients SHOULD wait before attempting the operation again.
+
+## ErrorResponse : Object
+
+Property | Type | Required | Description
+-------- | ---- | -------- | -----------
+`error` | Error | ✔ | The error object.
+
+## Error : Object
+
+Property | Type | Required | Description
+-------- | ---- | -------- | -----------
+`code` | String | ✔ | One of a server-defined set of error codes.
+`message` | String | ✔ | A human-readable representation of the error.
+`target` | String | | The target of the error.
+`details` | Error[] | | An array of details about specific errors that led to this reported error.
+`innererror` | InnerError | | An object containing more specific information than the current object about the error.
+
+## InnerError : Object
+
+Property | Type | Required | Description
+-------- | ---- | -------- | -----------
+`code` | String | | A more specific error code than was provided by the containing error.
+`innererror` | InnerError | | An object containing more specific information than the current object about the error.
+
+## Examples
+
+Example of "innererror":
+
+```json
+{
+ "error": {
+ "code": "unauthorized",
+ "message": "Previous passwords may not be reused",
+ "target": "password",
+ "innererror": {
+ "code": "passwordError",
+ "innererror": {
+ "code": "passwordDoesNotMeetPolicy",
+ "minLength": "6",
+ "maxLength": "64",
+ "characterTypes": ["lowerCase","upperCase","number","symbol"],
+ "minDistinctCharacterTypes": "2",
+ "innererror": {
+ "code": "passwordReuseNotAllowed"
+ }
+ }
+ }
+ }
+}
+```
+
+In this example, the most basic error code is "unauthorized", but for clients that are interested, there are more specific error codes in "innererror."
+The "passwordReuseNotAllowed" code may have been added by the service at a later date, having previously only returned "passwordDoesNotMeetPolicy."
+Existing clients do not break when the new error code is added, but new clients MAY take advantage of it.
+The "passwordDoesNotMeetPolicy" error also includes additional name/value pairs that allow the client to determine the server's configuration, validate the user's input programmatically, or present the server's constraints to the user within the client's own localized messaging.
+
+Example of "details":
+
+```json
+{
+ "error": {
+ "code": "badRequest",
+ "message": "Multiple errors in ContactInfo data",
+ "target": "contactInfo",
+ "details": [
+ {
+ "code": "nullValue",
+ "target": "phoneNumber",
+ "message": "Phone number must not be null"
+ },
+ {
+ "code": "nullValue",
+ "target": "lastName",
+ "message": "Last name must not be null"
+ },
+ {
+ "code": "malformedValue",
+ "target": "address",
+ "message": "Address is not valid"
+ }
+ ]
+ }
+}
+```
+
+In this example there were multiple problems with the request, with each individual error listed in "details."
diff --git a/graph/articles/naming.md b/graph/articles/naming.md
new file mode 100644
index 00000000..0489436e
--- /dev/null
+++ b/graph/articles/naming.md
@@ -0,0 +1,99 @@
+# Naming
+
+## 1. Approach
+
+Naming policies should aid developers in discovering functionality without having to constantly refer to documentation.
+Use of common patterns and standard conventions greatly aids developers in correctly guessing common property names and meanings.
+Services SHOULD use verbose naming patterns and MUST NOT use abbreviations other than acronyms that are the dominant mode of expression in the domain being represented by the API, (e.g. Url).
+
+## 2. Casing
+
+- Acronyms SHOULD follow the casing conventions as though they were regular words (e.g. Url).
+- All identifiers including namespaces, entityTypes, entitySets, properties, actions, functions and enumeration values MUST use lowerCamelCase.
+- HTTP headers are the exception and SHOULD use standard HTTP convention of Capitalized-Hyphenated-Terms.
+
+## 3. Names to avoid
+
+Certain names are so overloaded in API domains that they lose all meaning or clash with other common usages in domains that cannot be avoided when using REST APIs, such as OAUTH.
+Services SHOULD NOT use the following names:
+
+- Context
+- Scope
+- Resource
+
+## 4. Forming compound names
+
+- Services SHOULD avoid using articles such as 'a', 'the', 'of' unless needed to convey meaning.
+ - e.g. names such as aUser, theAccount, countOfBooks SHOULD NOT be used, rather user, account, bookCount SHOULD be preferred.
+- Services SHOULD add a type to a property name when not doing so would cause ambiguity about how the data is represented or would cause the service not to use a common property name.
+- When adding a type to a property name, services MUST add the type at the end, e.g. createdDateTime.
+
+## 5. Identity properties
+
+- Services MUST use string types for identity properties.
+- For OData services, the service MUST use the OData @id property to represent the canonical identifier of the resource.
+- Services MAY use the simple 'id' property to represent a local or legacy primary key value for a resource.
+- Services SHOULD use the name of the relationship postfixed with 'Id' to represent a foreign key to another resource, e.g. subscriptionId.
+ - The content of this property SHOULD be the canonical ID of the referenced resource.
+
+## 6. Date and time properties
+
+- For properties requiring both date and time, services MUST use the suffix 'DateTime'.
+- For properties requiring only date information without specifying time, services MUST use the suffix 'Date', e.g. birthDate.
+- For properties requiring only time information without specifying date, services MUST use the suffix 'Time', e.g. appointmentStartTime.
+
+## 7. Name properties
+
+- For the overall name of a resource typically shown to users, services MUST use the property name 'displayName'.
+- Services MAY use other common naming properties, e.g. givenName, surname, signInName.
+
+## 8. Collections and counts
+
+- Services MUST name collections as plural nouns or plural noun phrases using correct English.
+- Services MAY use simplified English for nouns that have plurals not in common verbal usage.
+ - e.g. schemas MAY be used instead of schemata.
+- Services MUST name counts of resources with a noun or noun phrase suffixed with 'Count'.
+
+## 9. Common property names
+
+Where services have a property, whose data matches the names below, the service MUST use the name from this table.
+This table will grow as services add terms that will be more commonly used.
+Service owners adding such terms SHOULD propose additions to this document.
+
+| | |
+|-------------------- | - |
+ attendees |
+ body |
+ completedDateTime | **NOTE** completionDateTime may be used for cases where the timestamp represents a point in the future |
+ createdDateTime |
+ childCount |
+ children |
+ contentUrl |
+ country |
+ createdBy |
+ displayName |
+ errorUrl |
+ eTag |
+ event |
+ expirationDateTime |
+ givenName |
+ jobTitle |
+ kind |
+ id |
+ lastModifiedDateTime |
+ location |
+ memberOf |
+ message |
+ name |
+ owner |
+ people |
+ person |
+ postalCode |
+ photo |
+ preferredLanguage |
+ properties |
+ signInName |
+ surname |
+ tags |
+ userPrincipalName |
+ webUrl |
diff --git a/graph/nullable.md b/graph/articles/nullable.md
similarity index 90%
rename from graph/nullable.md
rename to graph/articles/nullable.md
index 7e581620..f9ffcc20 100644
--- a/graph/nullable.md
+++ b/graph/articles/nullable.md
@@ -26,7 +26,7 @@ Below are some examples of nullable and non-nullable properties.
## HTTP Requests
-### {1} Create a servicePrincipal with no properties
+### 1. Create a servicePrincipal with no properties
```HTTP
POST /servicePrincipals
@@ -40,7 +40,7 @@ POST /servicePrincipals
}
```
-### {2} Create a servicePrincipal without a display name
+### 2. Create a servicePrincipal without a display name
```HTTP
POST /servicePrincipals
@@ -62,7 +62,7 @@ Notes:
2. `foo` has the default value as specified by its `DefaultValue` attribute in the CSDL
3. `bar` has the default value as specified by its `DefaultValue` attribute in the CSDL
-### {3} Update the display name of a service principal to null
+### 3. Update the display name of a service principal to null
```HTTP
PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
@@ -81,7 +81,7 @@ PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
Notes:
1. `displayName` cannot be set to `null` because it has be marked with `Nullable="false"` in the CSDL.
-### {4} Update the display name of a service principal
+### 4. Update the display name of a service principal
```HTTP
PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
@@ -102,7 +102,7 @@ Notes:
1. `displayName` can be set to any value other than `null`
2. The response body here is provided for clarity, and is not part of the guidance itself. The [OData v4.01 standard](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#sec_UpdateanEntity) states that the workload can decide the behavior.
-### {5} Update the foo property of a service principal to null
+### 5. Update the foo property of a service principal to null
```HTTP
PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
@@ -123,7 +123,7 @@ Notes:
1. `foo` can be set to `null` because it has be marked with `Nullable="true"` in the CSDL.
2. The response body here is provided for clarity, and is not part of the guidance itself. The [OData v4.01 standard](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#sec_UpdateanEntity) states that the workload can decide the behavior.
-### {6} Update the foo property of a service principal to a non-default value
+### 6. Update the foo property of a service principal to a non-default value
```HTTP
PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
@@ -144,7 +144,7 @@ Notes:
1. `foo` can be set to `something other than testval`
2. The response body here is provided for clarity, and is not part of the guidance itself. The [OData v4.01 standard](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#sec_UpdateanEntity) states that the workload can decide the behavior.
-### {7} Update the bar property of a service principal to null
+### 7. Update the bar property of a service principal to null
```HTTP
PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
@@ -163,7 +163,7 @@ PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
Notes:
1. `bar` cannot be set to `null` because it has be marked with `Nullable="false"` in the CSDL.
-### {8} Update the bar property of a service principal to a non-default value
+### 8. Update the bar property of a service principal to a non-default value
```HTTP
PATCH /servicePrincipals/00000000-0000-0000-0000-000000000001
@@ -184,7 +184,7 @@ Notes:
1. `bar` can be set to `a new bar`
2. The response body here is provided for clarity, and is not part of the guidance itself. The [OData v4.01 standard](https://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part1-protocol.html#sec_UpdateanEntity) states that the workload can decide the behavior.
-### {9} Create a service principal while customizing the display name
+### 9. Create a service principal while customizing the display name
```HTTP
POST /servicePrincipals
{
@@ -206,7 +206,7 @@ Notes:
2. `foo` has the default value as specified by its `DefaultValue` attribute in the CSDL
3. `bar` has the default value as specified by its `DefaultValue` attribute in the CSDL
-### {10} Create a service principal with a null display name
+### 10. Create a service principal with a null display name
```HTTP
POST /servicePrincipals
{
@@ -225,7 +225,7 @@ POST /servicePrincipals
Notes:
1. `displayName` isn't required to create a new `servicePrincipal`, but it *can* be provided; it *cannot* be provided as `null` because the property was marked with `Nullable="false"`
-### {11} Create a service principal with a value for the foo property
+### 11. Create a service principal with a value for the foo property
```HTTP
POST /servicePrincipals
{
@@ -247,7 +247,7 @@ Notes:
2. `foo` isn't required to create a new `servicePrincipal`, but it *can* be provided; this is orthogonal to whether or not the property has `Nullable="true"` or `Nullable="false"`.
3. `bar` has the default value as specified by its `DefaultValue` attribute in the CSDL
-### {12} Create a service principal with null for the foo property
+### 12. Create a service principal with null for the foo property
```HTTP
POST /servicePrincipals
{
@@ -269,7 +269,7 @@ Notes:
2. `foo` isn't required to create a new `servicePrincipal`, but it *can* be provided; because the property has `Nullable="true"`, a `null` value can be provided for it.
3. `bar` has the default value as specified by its `DefaultValue` attribute in the CSDL
-### {13} Create a service principal with a value for the bar property
+### 13. Create a service principal with a value for the bar property
```HTTP
POST /servicePrincipals
{
@@ -291,7 +291,7 @@ Notes:
2. `foo` has the default value as specified by its `DefaultValue` attribute in the CSDL
3. `bar` isn't required to create a new `servicePrincipal`, but it *can* be provided; this is orthogonal to whether or not the property has `Nullable="true"` or `Nullable="false"`.
-### {14} Create a service principal with null for the bar property
+### 14. Create a service principal with null for the bar property
```HTTP
POST /servicePrincipals
{
diff --git a/graph/patterns/default-properties.md b/graph/patterns/default-properties.md
new file mode 100644
index 00000000..879612f7
--- /dev/null
+++ b/graph/patterns/default-properties.md
@@ -0,0 +1,201 @@
+# Default properties
+
+Microsoft Graph API Design Pattern
+
+*The default properties pattern allows API producers to omit specific properties from the response unless they are explicitly requested using `$select`.*
+
+## Problem
+
+API designers want to control the set of properties that their entities return by default, when the incoming request does not specify a `$select`. This can be desirable when an entity type has many properties or an API producer needs to add properties that are computationally expensive to return by default.
+
+## Solution
+
+For incoming requests targeting an entity type where the caller does not specify a `$select` clause, API producers **may** return a subset of the entity type's properties, omitting computationally expensive properties. To get the non-default properties of an entity type, callers must explicitly request them using `$select`.
+
+The pattern also uses an instance annotation to inform callers that other properties are also available. The same annotation is also used to encourage callers to use `$select`.
+
+## When to use this pattern
+
+API producers should use this pattern when adding expensive or non-performant properties to an existing entity type, or when adding properties to an entity type that has already grown too large (with more than 20 properties).
+
+## Issues and considerations
+
+- Do **not** rely on the `ags:Default` schema annotation for default properties functionality, as this is a legacy implementation. Returning default properties **must** be implemented by API producers.
+- Changing a default property to non-default is considered a breaking change.
+- One of the challenges with default properties is informing developers that the response does not contain the full set of properties. To solve for this discovery problem, if the response contains default properties only, then:
+ - the response **must** contain a `@microsoft.graph.tips` instance annotation.
+ - the `@microsoft.graph.tips` instance annotation **must** only be emitted if the client uses "developer mode" via the `Prefer: ms-graph-dev-mode` HTTP request header. It is expected that this header will only be used by client developer and scripting tools like Graph Explorer, the Microsoft Graph Postman collections, and Microsoft Graph PowerShell.
+ - the `@microsoft.graph.tips` instance annotation value **must** contain "This request only returns a subset of the resource's properties. Your app will need to use $select to return non-default properties. To find out what other properties are available for this resource see https://learn.microsoft.com/graph/api/resources/{entityTypeName}".
+- Callers must be able to use `$filter` with non-default properties, even though they won't show up by default in the response.
+
+Additionally, for incoming requests targeting an entity type where the caller does not specify a `$select` clause, the API Gateway Service will inject a `@microsoft.graph.tips` instance annotation, informing callers to use $select, when in "developer mode".
+API producers who use [response passthrough](https://dev.azure.com/msazure/One/_wiki/wikis/Microsoft%20Graph%20Partners/391069/Enabling-response-passthrough) must also implement this behavior, supplying the same information as shown in the [examples section below](#calling-an-api-without-using-select).
+
+## Examples
+
+In this example we'll use the following `channel` entity type.
+
+```xml
+
+
+
+
+
+
+
+
+
+
+
+
+```
+
+In this scenario, the API producer wants to add the `moderationSettings` property to the `channel` entity type.
+But when paging through 1000 channels at a time, this additional property will introduce a considerable increase in the response times.
+The API producer will use the default properties pattern here, and **not** return `moderationSettings` by default.
+
+### Calling an API with default properties
+
+In this example, the caller, using Graph Explorer, does not use $select, and the API returns just the default properties.
+
+#### Request
+
+```http
+GET /teams/{id}/channels
+Prefer: ms-graph-dev-mode
+```
+
+#### Response
+
+```http
+200 ok
+Content-type: application/json
+```
+
+```json
+{
+ "@odata.context": "https://graph.microsoft.com/beta/$metadata#Collection(microsoft.graph.channel)",
+ "@microsoft.graph.tips": "This request only returns a subset of the resource properties. Your app will need to use $select to return non-default properties. To find out what other properties are supported for this resource, please see the Properties section in https://learn.microsoft.com/graph/api/resources/channel.",
+ "value": [
+ {
+ "displayName": "My First Shared Channel",
+ "description": "This is my first shared channels",
+ "id": "19:PZC_kAPAm12RPBMkEaJyXaY_d2PE6mJV6MzO1EiCbnk1@thread.tacv2",
+ "membershipType": "shared",
+ "email": "someemail@dot.com",
+ "webUrl": "webUrl-value",
+ "filesFolderWebUrl": "sharePointUrl-value",
+ "tenantId": "tenantId-value",
+ "isFavoriteByDefault": null,
+ "createdDateTime": "2019-08-07T19:00:00Z"
+ },
+ {
+ "displayName": "My Second Private Channel",
+ "description": "This is my second shared channels",
+ "id": "19:PZC_kAPAm12RPBMkEaJyXaY_d2PE6mJV6MzO1EiCbnk2@thread.tacv2",
+ "membershipType": "private",
+ "email": "someemail2@dot.com",
+ "webUrl": "webUrl-value2",
+ "filesFolderWebUrl": "sharePointUrl-value2",
+ "tenantId": "tenantId-value",
+ "isFavoriteByDefault": null,
+ "createdDateTime": "2019-08-09T19:00:00Z"
+ }
+ ]
+}
+```
+
+In the response, we can see that `moderationSettings` is not being returned. Additionally, the API producer is returning a `tips` instance annotation, informing the caller that this response only returns default properties, how to get the non-default properties, and where to find information about this type's properties. The `tips` instance annotation is only emitted if the `Prefer: ms-graph-dev-mode` HTTP request header is present.
+
+### Calling an API with default properties and $select
+
+In this example, the caller needs `moderationSettings` for their API scenario. They try this out in Graph Explorer first.
+
+#### Request
+
+```http
+GET /teams/{id}/channels?$select=id,membershipType,moderationSettings
+Prefer: ms-graph-dev-mode
+```
+
+#### Response
+
+```http
+200 ok
+Content-type: application/json
+```
+
+```json
+{
+ "@odata.context": "https://graph.microsoft.com/beta/$metadata#Collection(microsoft.graph.channel)",
+ "value": [
+ {
+ "id": "19:PZC_kAPAm12RPBMkEaJyXaY_d2PE6mJV6MzO1EiCbnk1@thread.tacv2",
+ "membershipType": "shared",
+ "channelModerationSettings": {
+ "userNewMessageRestriction": "everyone",
+ "replyRestriction": "everyone",
+ "allowNewMessageFromBots": true,
+ "allowNewMessageFromConnectors": true
+ }
+ },
+ {
+ "id": "19:PZC_kAPAm12RPBMkEaJyXaY_d2PE6mJV6MzO1EiCbnk2@thread.tacv2",
+ "membershipType": "private",
+ "channelModerationSettings": {
+ "userNewMessageRestriction": "moderators",
+ "replyRestriction": "authorAndModerators",
+ "allowNewMessageFromBots": true,
+ "allowNewMessageFromConnectors": true
+ }
+ }
+ ]
+}
+```
+
+In this case, because the request has a `$select`, the `tips` instance annotation is not emitted.
+
+### Calling an API without using $select
+
+The caller makes a `GET` request without $select, to an API that doesn't have any default properties, via Graph Explorer.
+
+#### Request
+
+```http
+GET /me/todo/lists
+Prefer: ms-graph-dev-mode
+```
+
+#### Response
+
+```http
+200 ok
+Content-type: application/json
+```
+
+```json
+{
+ "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users('99a6e897-8c54-4354-a739-626fbe28ed78')/todo/lists",
+ "@microsoft.graph.tips": "Use $select to choose only the properties your app needs, as this can lead to performance improvements. For example: GET me/todo/lists?$select=displayName,isOwner",
+ "value": [
+ {
+ "@odata.etag": "W/\"c5yMNreru0OMO71/IwuKGQAG6WUnjQ==\"",
+ "displayName": "Tasks",
+ "isOwner": true,
+ "isShared": false,
+ "wellknownListName": "defaultList",
+ "id": "AAMkADU3NTBhNWUzLWE0MWItNGViYy1hMTA0LTkzNjRlYTA2ZWI2ZAAuAAAAAAAFup0i-hqtR5N14AJlh2qTAQATqGUvrHrTEbWPAKDJQ2mMAAACWIG1AAA="
+ },
+ {
+ "@odata.etag": "W/\"c5yMNreru0OMO71/IwuKGQAG6WUnmQ==\"",
+ "displayName": "Outlook Commitments",
+ "isOwner": true,
+ "isShared": false,
+ "wellknownListName": "none",
+ "id": "AQMkADU3NTBhNWUzLWE0MWItNGViYy1hMTA0LTkzNjRlYTA2ZWI2ZAAuAAADBbqdIv4arUeTdeACZYdqkwEAc5yMNreru0OMO71-IwuKGQABWbOTpQAAAA=="
+ }
+ ]
+}
+```
+
+Notice how for this scenario, where there are no default properties and the caller does not use `$select`, there's a `tips` instance annotation, encouraging the app developer to use `$select`. This `tips` annotation is automatically added to the response by the API gateway service, as long as the workload service doesn't use response passthrough (in which case it is the responsibility of the workload service).
diff --git a/graph/patterns/dictionary.md b/graph/patterns/dictionary.md
index 3b70af4a..234aebc3 100644
--- a/graph/patterns/dictionary.md
+++ b/graph/patterns/dictionary.md
@@ -37,30 +37,42 @@ For more information, see the [OData reference](https://github.com/oasis-tcs/oda
## Examples
-### Declaring a string dictionary
+### String dictionary
+
+#### CSDL declaration
The following example demonstrates defining a dictionary that can contain string values.
```xml
-
-
-
- Edm.String
-
-
-
+
+
+
+
+
+
+
+
+
+ Edm.String
+
+
+
+
```
-### Defining a dictionary property
+Please note that schema validation will fail due to the casing of `Dictionary`.
+This warning should be suppressed.
+
+#### Defining a dictionary property
The following example shows defining a dictionary property, "userTags", on the item entity type.
```xml
...
-
+
```
-### Reading a dictionary
+#### Reading a dictionary
Dictionaries are represented in JSON payloads as a JSON object, where the property names are comprised of the keys and their values are the corresponding key values.
The following example shows reading an item with a dictionary property named "userTags":
@@ -80,7 +92,7 @@ Response:
}
```
-### Setting a dictionary value
+#### Setting a dictionary value
The following example shows setting a dictionary value. If "hairColor" already exists, it is updated, otherwise it is added.
```http
@@ -92,7 +104,7 @@ PATCH /item/userTags
}
```
-### Deleting a dictionary value
+#### Deleting a dictionary value
A dictionary value can be removed by setting the value to null.
```http
PATCH /item/userTags
@@ -103,34 +115,43 @@ PATCH /item/userTags
}
```
-### Declaring a complex typed dictionary
+### Complex typed dictionary
+
+#### CSDL declaration
Dictionaries can also contain complex types whose values may be constrained to a particular set of complex types.
The following example defines a complex type **roleSettings**, an **assignedRoleGroupDictionary** that contains **roleSettings**, and an **assignedRoles** property that uses the dictionary..
```xml
-
- ...
-
-
-
-
-
-
-
-
-
-
-
- microsoft.graph.roleSettings
-
-
-
+
+
+
+
+
+
+
+ ...
+
+
+
+
+
+
+
+
+
+ of roleSettings
+ keyed by name of roleGroup. -->
+
+
+ microsoft.graph.roleSettings
+
+
+
+
```
-### Reading a entity with a complex-typed dictionary
+#### Reading a entity with a complex-typed dictionary
The following example illustrates reading an entity containing the complex-typed dictionary "assignedRoles".
@@ -158,7 +179,7 @@ Response:
}
```
-### Reading the dictionary property
+#### Reading the dictionary property
The following example shows getting just the "assignedRoles" dictionary property.
```HTTP
diff --git a/graph/patterns/enums.md b/graph/patterns/enums.md
index a47de3ea..080435af 100644
--- a/graph/patterns/enums.md
+++ b/graph/patterns/enums.md
@@ -100,6 +100,8 @@ but it is also open for future scenarios:
Additionally speaking, depending on the situation, a nullable enum can very likely be avoided by adding a `none` member.
+If used, `EnumType` names should be singular if the are non-flags enums, and the names should be plural if they are flags enums.
+
#### Flag Enums or Collection of Enums
In case an enum can have multiple values at the same time the tentation is to model the property as a collection of Enums:
@@ -127,3 +129,15 @@ However, [Flagged Enums](https://docs.oasis-open.org/odata/odata-csdl-xml/v4.01/
With such enum, customers can select multiple values in a single field:
`displayMethod = tip | alert`
+
+In cases where two properties want to use the same *conceptual* `EnumType`, but one property is a collection while the other is single-values, the model should define *two* separate `EnumType`s, one being a non-flags enum with a singular name and the other marked as a flags enum with its name being the plural form of the non-flags enum.
+
+#### Flag enum + non-flag enum
+
+There are occasions where one API will want to use a non-flag enum, but another API will want a flags enum.
+For example, the `displayMethod` example above may have one API that is configuring which display methods to use, and another API which is configuring that particular display method.
+In this case, the first API will want a flags enum, but the second API will want to only allow configuring one display method at a time, and will therefore prefer a non-flags enum.
+
+Two enum types should be defined, one as a flags enum and the other as a non-flags enum.
+The flags enum should be named such that it is plural, and the non-flags enum should be named such that it is singular.
+The two types should be kept in sync with each other.
diff --git a/graph/patterns/long-running-operations.md b/graph/patterns/long-running-operations.md
index cd4a8905..1f664740 100644
--- a/graph/patterns/long-running-operations.md
+++ b/graph/patterns/long-running-operations.md
@@ -46,10 +46,6 @@ The RELO pattern is the preferred pattern for long running operations and should
used wherever possible. The pattern avoids complexity, and consistent resource
presentation makes things simpler for our users and tooling chain.
-In general, Microsoft Graph API guidelines for long running operations follow [Microsoft REST API
-Guidelines](https://github.com/microsoft/api-guidelines/blob/vNext/Guidelines.md#13-long-running-operations).
-There are some deviations from the base guidelines where Microsoft Graph API standards require that you do one of the following:
-
- For the RELO pattern, you should return the Location header that indicates the location of the resource.
- The API response says the targeted resource is being created by returning a 201 status code and the resource URI is provided in the Location header, but the response indicates that the request is not completed by including "Provisioning" status.
diff --git a/graph/patterns/namespace.md b/graph/patterns/namespace.md
index 46d282cc..e4b6fef8 100644
--- a/graph/patterns/namespace.md
+++ b/graph/patterns/namespace.md
@@ -16,31 +16,39 @@ API designers can use the namespace attribute of the CSDL schema to declare a
namespace and logically organize related API entities in the Microsoft Graph metadata.
```XML
-
+
...
```
A public namespace must contain the `microsoft.graph.` prefix and be presented in camel
-case; that is, `microsoft.graph.myNamespace`.
+case; that is, `microsoft.graph.myNamespace`. Elements defined in namespaces not prefixed
+with `microsoft.graph` will be mapped to the public `microsoft.graph` namespace.
+
+Namespaces should not include more than two segments following the `microsoft.graph` prefix;
+that is, `microsoft.graph.myNamespace.mySubNamespace`.
+
+Public namespaces must define an alias, and that alias must be the concatenation of
+the segments following the `microsoft.graph` prefix with proper camel casing rules applied;
+that is, `myNamespaceMySubNamespace`.
When type casting is required in the API query, request, or response, a fully
-qualified type name is represented as concatenation of a namespace and a type
-name. For a consistent user experience, namespaces MUST be aligned with the corresponding API category path segment.
+qualified type name is represented as concatenation of the namespace or alias,
+followed by a dot (`.`) and the type name.
## When to use this pattern
API resource grouping creates a user-friendly experience, keeping all resources for a specific feature close together and limiting the length of IDE prompts such as auto-complete in some programming languages.
-We recommend that a new namespace be aligned with a top-level API category.
+For a consistent user experience, new namespace should be aligned with a top-level API category.
## Issues and considerations
-- Microsoft Graph consistency requirements discourage using the same type names for different concepts even within different namespaces. Microsoft Graph type names must be descriptive and unique within the API surface without requiring full qualification.
+- Microsoft Graph consistency requirements discourage using the same type names for different concepts even within different namespaces. Microsoft Graph type names must be descriptive and should represent a single concept across the API Surface.
- A namespace must be consistent with an API category in the navigation path according to [Microsoft Graph REST API Guidelines](../GuidelinesGraph.md#uniform-resource-locators-urls).
-- When type name is ambiguous and requires a namespace qualifier, changing a namespace is a breaking change.
+- Changing a namespace prefixed with `microsoft.graph`, or moving types between, into, or out of a namespace prefixed with `microsoft.graph`, is a breaking change.
- To extend a type in a different schema, a service must declare that schema and the type in it. This is conceptually similar to .NET partial types.
@@ -51,17 +59,19 @@ We recommend that a new namespace be aligned with a top-level API category.
- Microsoft Graph has some predefined constraints for declared namespaces:
- All public namespaces must have the prefix `microsoft.graph`.
+
+ - Public namespaces must declare an alias that is the concatenation of the segments following the `microsoft.graph` prefix.
+
+ - At most, two levels of nesting below `microsoft.graph` is recommended.
- - Only one level of nesting deeper than `microsoft.graph` is supported.
-
- - If a namespace does not begin with the `microsoft.graph` prefix, all types in the schema are coerced into the main `microsoft.graph` namespace.
+ - If a namespace does not begin with the `microsoft.graph` prefix, all types in the schema are mapped into the public `microsoft.graph` namespace.
## Examples
### Namespace and type declarations
```XML
-”\>
+”\>
…
@@ -88,7 +98,7 @@ declarations) to match this example.
-
+
@@ -111,4 +121,4 @@ declarations) to match this example.
-```
+```
\ No newline at end of file
diff --git a/graph/patterns/navigation-property.md b/graph/patterns/navigation-property.md
index 3b06d5e1..6551e2a0 100644
--- a/graph/patterns/navigation-property.md
+++ b/graph/patterns/navigation-property.md
@@ -35,12 +35,15 @@ These relationships can be described in CSDL as follows:
## Issues and Considerations
-------------------------
-In the current Microsoft Graph implementation, there are some limitations on the use of navigation properties that cross between backend services. These limitations are being eliminated over time, but it will be necessary to ensure support for any particular scenario. [Limitations of the current implementation](https://dev.azure.com/msazure/One/_wiki/wikis/Microsoft%20Graph%20Partners/354352/Cross-workload-navigations?anchor=supported-scenarios) are documented internally.
+In the current Microsoft Graph implementation, there are scenarios which use navigation properties that cross backend services that have automatic support; there are also some limitations for other scenarios. These limitations are being eliminated over time, but it will be necessary to ensure support for any particular scenario. [Automatic support and limitations of the current implementation](https://dev.azure.com/msazure/One/_wiki/wikis/Microsoft%20Graph%20Partners/354352/Cross-workload-navigations?anchor=supported-scenarios) are documented internally.
Navigation properties defined within an entity are not returned by default when retreiving the representation of an entity unless explicity desired by a service. The API can consumer can use the `expand` query parameterm, where supported, to retreive both the source and the target entity of the relationship in a single request.
Implementing support for accessing the "$ref" of a navigation property allows a caller to return just the URL of related resource. e.g. `/user/23/manager/$ref`. This is useful when a client wishes to identify the related resource but doesn't need all of its properties.
+The strongly-typed nature of navigation properties is valuable for backend services and for client applications, when compared with the weakly-typed foreign key property.
+Strong typing allows some documentation and visualizations to be automatically generated, it allows SDK generation, and it allows some automated client code generation; it also prevents the need to store duplicate data on the service side and as a result has improved data consistency across APIs since the duplicate data does not need to be regularly refreshed.
+
## When to Use this Pattern
------------------------
diff --git a/graph/patterns/subtypes.md b/graph/patterns/subtypes.md
index c5c6a098..aad10593 100644
--- a/graph/patterns/subtypes.md
+++ b/graph/patterns/subtypes.md
@@ -2,7 +2,7 @@
Microsoft Graph API Design Pattern
-*A frequent pattern in Microsoft Graph is to have a small type hierarchy, a base type with a few subtypes. This lets us model collections of resources that have slightly different metadata and behavior.*
+*A frequent pattern in Microsoft Graph is to have a small type hierarchy, a base type with a few subtypes. This lets us model collections of resources that have slightly different properties and behavior.*
## Problem
@@ -27,9 +27,9 @@ You can consider related patterns such as [facets](./facets.md) and [flat bag of
## Issues and considerations
When introducing a new subtype to the hierarchy, developers need to ensure that
-the new subtype doesn't change the semantic of the type hierarchy with its implicit constraints.
+the new subtype doesn't change the semantic of the type hierarchy or collections of the specified base type with implicit constraints.
-To retrieve properties specific for a derived type, an API request URL might need to include casting to the derived type. If the type hierarchy is very deep, then the resulting URL might become very long and not easily readable.
+To reference properties specific to a derived type, an API request URL might need to include a segment casting to the derived type. If the type hierarchy is very deep, then the resulting URL might become very long and not easily readable.
There are a few considerations to take into account when new subtypes are introduced:
@@ -52,65 +52,99 @@ and groups stored in Azure Active Directory. Because any directoryObject object
-
-
+
+
```
Groups and users are derived types and modeled as follows:
```XML
-
-
+
+ ...
-
-…
+
+ ...
```
An API request to get members of a group returns a heterogeneous collection of
users and groups where each element can be a user or a group, and has an
-additional property @odata.type for a variant subtype:
+additional `@odata.type` property that specifies the subtype:
```
-GET https://graph.microsoft.com/v1.0/groups/a94a666e-0367-412e-b96e-54d28b73b2db/members?$select=id,displayName
+GET https://graph.microsoft.com/v1.0/groups/a94a666e-0367-412e-b96e-54d28b73b2db/members
-Response payload shortened for readability:
+Response payload shortened for readability. The deletedDateTime property from the base type is a non-default property and is only returned if explicitly requested.
{
"@odata.context":
-"https://graph.microsoft.com/v1.0/\$metadata\#directoryObjects",
- "value": [
- {
+"https://graph.microsoft.com/v1.0/$metadata#directoryObjects",
+ "value": [
+ {
"@odata.type": "#microsoft.graph.user",
"id": "37ca648a-a007-4eef-81d7-1127d9be34e8",
- "displayName": "John Cob"
+ "jobTitle": "CEO",
+ ...
},
{
"@odata.type": "#microsoft.graph.group",
"id": "45f25951-d04f-4c44-b9b0-2a79e915658d",
- "displayName": "Department 456"
+ "description": "Microsoft Graph API Reviewers",
+ ...
},
...
- ]
+ ]
+}
+```
+
+Addressing a property of the subtype, for example, in `$filter` or `$select`, requires prefixing the property with the fully-qualified name of the subtype (or type derived from the subtype) on which it is defined. To filter on the `jobTitle` for the user type, you need to qualify the property with `microsoft.graph.user`.
+
+The following query returns all groups that are members of group a94a666e-0367-412e-b96e-54d28b73b2db, as well as users that are members and whose jobTitle is CEO.
+
+```
+GET https://graph.microsoft.com/v1.0/groups/a94a666e-0367-412e-b96e-54d28b73b2db/members?$filter=microsoft.graph.user/jobTitle eq 'CEO'
+
+Response payload shortened for readability:
+
+{
+ "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#directoryObjects",
+ "value": [
+ {
+ "@odata.type": "#microsoft.graph.user",
+ "id": "37ca648a-a007-4eef-81d7-1127d9be34e8",
+ "jobTitle": "CEO",
+ ...
+ },
+ {
+ "@odata.type": "#microsoft.graph.group",
+ "id": "45f25951-d04f-4c44-b9b0-2a79e915658d",
+ "description": "Microsoft Graph API Reviewers",
+ ...
+ },
+ ...
+ ]
}
```
-An API request for a subtype-specific property requires type casting to the subtype; that is, to retrieve the jobTitle property enabled for the user type, you need to cast from the directoryObject collection items to the `microsoft.graph.group` derived type.
+An entire collection can be cast to a particular subtype by appending the fully-qualified subtype name to the URL. Doing so filters the collection to members of (or derived from) that particular subtype, and makes the properties of that subtype available without casting. In this case, the `@odata.type` attribute is not returns for records of the specified subtype because the `@odata.context` indicates that the entire collection is consists of the particular subtype. Types derived from that subtype do still have the `@odata.type` attribute.
+
+The following query returns only users that are members of group a94a666e-0367-412e-b96e-54d28b73b2db and whose jobTitle is CEO.
```
-GET https://graph.microsoft.com/v1.0/groups/a94a666e-0367-412e-b96e-54d28b73b2db/members/microsoft.graph.user?$select=displayName,jobTitle
+GET https://graph.microsoft.com/v1.0/groups/a94a666e-0367-412e-b96e-54d28b73b2db/members/microsoft.graph.user?$filter=jobTitle eq 'CEO'
Response payload shortened for readability:
{
- "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users(displayName,jobTitle)",
+ "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users",
"value": [
{
- "displayName": "John Cob",
- "jobTitle": "RESEARCHER II"
+ "id": "37ca648a-a007-4eef-81d7-1127d9be34e8",
+ "jobTitle": "CEO",
+ ...
},
...
]
@@ -124,9 +158,7 @@ POST https://graph.microsoft.com/v1.0/directoryObjects
{
"@odata.type": "#microsoft.graph.group",
- "displayName": "Library Assist",
- "mailEnabled": false,
- "mailNickname": "library",
- "securityEnabled": true
+ "description": "Microsoft Graph API Reviewers",
+ ...
}
```