FragLink enables Linked Data Fragments capabilities to your Server. It's not a server itself. Instead, it comes as a SpringBoot autoconfigure module that you can easily plug into your RDF Server.

Quick Start

FragLink is written in Java and makes use of the Spring Framework. Specifically, it is an autoconfigure module, which is supposed to be declared as a dependency in a SpringBoot (Server) project.

1. Create a SpringBoot project

This will be your Linked Data Fragment Server. It is strongly recommended to use Spring initializr to define the initial shape of the module (e.g., components, dependencies, frameworks, starters).

2. Maven repository and Fraglink dependency.

Then, once the project skeleton is created, open the pom.xml (in case you're using Gradle, there's a corresponding configuration) and add the following section:

<repositories>
  <repository>
    <id>fraglink-package-registry</id>
    <url>https://gitlab.com/api/v4/projects/52914288/packages/maven</url>
  </repository>
</repositories>

The snippet above declares the coordinates to the maven repository where the FragLink artifacts are hosted. Then, in the dependencies section:

<dependency>
  <groupId>com.spaziocodice.labs.rdf</groupId>
  <artifactId>fraglink-starter</artifactId>
  <version>1.1.2</version>
</dependency>

3. Configuration

Assuming you already set up everything in your SpringBoot module (e.g., dependencies and so on), here's the minimal configuration required by FragLink:

fraglink:
  base:
    url: https://fragments.yourproject.org  (this is an example)
  page:
    maxStatements: 50 (the maximum number of statements returned in response)
  dataset:
    name: "The dataset project/name" 
    description: "An optional description of the project."

4. Start

Start your server. After a few seconds, you should see the following messages:

... : <FRAGLINK-00001> : FragLink v1.1.2 has been enabled on this server.

The server is running: great! Linked Data Fragments are exposed through the root (/) REST endpoint. The endpoint template is

https://fragments.yourproject.org{subject, predicate, object, graph, page}

However, being a triple/quad pattern resolver, it doesn't still know how to fetch data. The default implementation is a simple NoOp, meaning no data is returned in response, only metadata. Here's an example (empty) response:

<https://fragments.yourproject.org/fragments#metadata> {
    <https://fragments.yourproject.org/fragments#dataset>
            a       <http://rdfs.org/ns/void#Dataset> , <http://www.w3.org/ns/hydra/core#Collection>;
            <http://rdfs.org/ns/void#subset>
                    <https://fragments.yourproject.org/fragments>;
            <http://www.w3.org/ns/hydra/core#search>
                    [ <http://www.w3.org/ns/hydra/core#mapping>
                              [ <http://www.w3.org/ns/hydra/core#property>
                                        <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject>;
                                <http://www.w3.org/ns/hydra/core#variable>
                                        "subject"
                              ];
                      <http://www.w3.org/ns/hydra/core#mapping>
                              [ <http://www.w3.org/ns/hydra/core#property>
                                        <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate>;
                                <http://www.w3.org/ns/hydra/core#variable>
                                        "predicate"
                              ];
                      <http://www.w3.org/ns/hydra/core#mapping>
                              [ <http://www.w3.org/ns/hydra/core#property>
                                        <http://www.w3.org/1999/02/22-rdf-syntax-ns#object>;
                                <http://www.w3.org/ns/hydra/core#variable>
                                        "object"
                              ];
                      <http://www.w3.org/ns/hydra/core#template>
                              "https://fragments.yourproject.org/fragments{?subject,predicate,object,page}";
                      <http://www.w3.org/ns/hydra/core#variableRepresentation>
                              <http://www.w3.org/ns/hydra/core#ExplicitRepresentation>
                    ] .
    
    <https://fragments.yourproject.org#dataset>
            a       <http://www.w3.org/ns/hydra/core#Collection>;
            <http://purl.org/dc/elements/1.1/description>
                    "An optional description of the dataset.";
            <http://purl.org/dc/elements/1.1/title>
                    "The Dataset project/name";
            <http://www.w3.org/ns/hydra/core#member>
                    <https://fragments.yourproject.org/fragments#dataset> .
    
    <https://fragments.yourproject.org/fragments#metadata>
            <http://xmlns.com/foaf/0.1/primaryTopic>
                    [ a <https://fragments.yourproject.org/fragments> ] .
    
    <https://fragments.yourproject.org/fragments>
            a       <http://www.w3.org/ns/hydra/core#PartialCollectionView>;
            <http://purl.org/dc/elements/1.1/description>
                    "Linked Data Fragment of Share-VDE dataset containing triples matching the pattern {?s ?p ?o ?q}"@en;
            <http://purl.org/dc/elements/1.1/source>
                    "https://fragments.yourproject.org/fragments#dataset";
            <http://purl.org/dc/elements/1.1/title>
                    "Linked Data Fragment of The Share-VDE Project Dataset"@en;
            <http://rdfs.org/ns/void#subset>
                    <https://fragments.yourproject.org/fragments>;
            <http://rdfs.org/ns/void#triples>
                    "0"^^<http://www.w3.org/2001/XMLSchema#long>;
            <http://www.w3.org/ns/hydra/core#firstPage>
                    <https://fragments.yourproject.org/fragments?page=1>;
            <http://www.w3.org/ns/hydra/core#itemsPerPage>
                    "50"^^<http://www.w3.org/2001/XMLSchema#int>;
            <http://www.w3.org/ns/hydra/core#totalItems>
                    "0"^^<http://www.w3.org/2001/XMLSchema#long> .
}

4. Linked Data Fragment Resolver

To create a valid binding in your project tied to your data source, you must create an implementation of

com.spaziocodice.labs.fraglink.service.impl.LinkedDataFragmentResolver

The interface contains a single method, which takes a triple/quad pattern in input and expects the list of matching triples in output.