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 recommendation, ccREL is based on the World-Wide Web Consortium's Resource Description Framework (RDF). 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.
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.