RDF

RDF (Resource Description Framework) is a W3C standard describing both an abstract structure for keeping track of information about a resource, and the concrete implementation of this structure serialized as an XML document.

RDF was originally the basis of the RSS standard, though some later versions of RSS (though not all, due to its forked development with different philosophies of different developers) are no longer based on RDF.

RDF can be used to express metadata about a particular thing and its relationships with other things. It is an important element of the Semantic Web project, intending to evolve the Web to a stage where it enables automatic processing of information in a rigorously-defined way.

Standards

 * W3C: RDF Vocabulary Description Language 1.0: RDF Schema (2004)
 * W3C: RDF/XML Syntax Specification (2004)
 * RFC 3870 (MIME type registration)

Other links

 * W3C RDF page
 * Wikipedia article