The cerretive common

[Chandanra65]

ccREL: The Creative Commons Rights Expression Language

Hal Abelson, Ben Adida, Mike Linksvayer, Nathan Yergler
[hal , ben,ml ,nathan] @creativecommons . org
Version 1.0 - March 3rd, 2008

1 Introduction

This paper introduces the Creative Commons Rights Expression Language (ccREL), the standard
recommended by Creative Commons (CC) for machine-readable expression of copyright licensing
terms and related information. ccREL and its description in this paper supersede all previous
Creative Commons recommendations for expressing licensing metadata. Like CC's previous rec
ommendation, ccREL is based on the World-Wide Web Consortium's Resource Description Frame
work (RDF).2 Compared to the previous recommendation, ccREL is intended to be both easier
for content creators and publishers to provide, and more convenient for user communities and tool
builders to consume, extend, and redistribute.3

Formally, ccREL is specified in an abstract syntax-free way, as an extensible set of properties to
be associated with a licensed documents. Publishers have wide discretion in their choice of syntax,
so long as the process for extracting the properties is discoverable and tool builders can retrieve the
properties of ccREL-compliant Web pages or embedded documents. We also recommend specific
concrete "default" syntaxes and embedding schemes for content creators and publishers who want
to use CC licenses without needing to be concerned about extraction mechanisms. The default
schemes are RDFa for HTML Web pages and resources referenced therein, and XMP for stand
alone media.

4

An Example. Using this new recommendation, an author can express Creative Commons struc
tured data in an HTML page using the following simple markup:

Information about Creative Commons is available on the web at http://creativecommons . org. ccREL is a
registered trademark of Creative Commons, see http://creativecommons . org/policies for details.

a wide Web. We provide a short

is a language for representing information about resources in the World
primer in this paper. Also, see the Web Consortium's RDF Web site at http://www.w3.org/RDF/.

ŠBy "publisher" we mean anyone who places CC-licensed material on the Internet. By “tool builders" we mean
people who write applications that are aware of the license information. Example tools might be search programs that
filter their results based on specific types of licenses, or user interfaces that display license information in particular

ways

RDFa is an emerging collection of attributes and processing rules for extending XHTML to support RDF.
See the W3C Working Draft "RDFa in XHTML: Syntax and Processing" at http://www.w3.org/TR/rdfa-syntax.
The "RDFa Primer: Embedding Structured Data in Web Pages," may be found at http://www.w3.org/TR/
xhtml-rdfa-primer. RDF/XML, described briefly below, is a method for expressing RDF in XML syntax. See
"RDF/XML Syntax Specification (Revised)," w3C Recommendation 10 February 2004 at http://www. w3.org/TR/
rdf-syntax- grammar/. XMP (Extended Metadata Plat form) is a labeling technology developed by Adobe, for em
bedding constrained RDF/XML within documents. See http://www. adobe . com/products/xmp/.

This work is licensed under a Creative Commons Attribution License, v3.0. The license is
available at http://creativecommons. org/licenses/by/3. 0/. Please provide attribution to
Creative Commons and the URL http://creat ivecommons. org/projects/ccREL.

This page, by

Lawrence Lessig
,

is licensed under a

Creative Commons Attribution License
.

From this markup, tools can easily and reliably determine that http://lessig . org/blog/ is li
censed under a CC Attribution License, v3.0, where attribution should be given to "Lawrence
Lessig" at the URL http://lessig . org/.

Structure of this Paper. This paper explains the design rationale for these recommendations
and illustrates some specific applications we expect ccREL to support. We begin with a review of
the original 2002 recommendation for Creative Commons metadata and we explain why, as Creative
Commons has grown, we have come to regard this as inadequate. We then introduce ccREL in
the syntax-free model: as a vocabulary of properties. Next, we describe the recommended concrete
syntaxes. In addition, we explain how other frameworks, such as microformats, can be made ccREL
compliant. Finally, we discuss specific use cases and the types of tools we hope to see built to take
advantage of ccREL.

2 Background on Creative Commons recommendations