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 (other serialization formats are also possible).

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.

RDFa is a related spec for linked data embedded within HTML.

Standards

 * W3C: RDF Vocabulary Description Language 1.0: RDF Schema (2004)
 * W3C: RDF/XML Syntax Specification (2004)
 * HTML+RDFa 1.1 W3C Proposed Recommendation 25 June 2013
 * RFC 3870 (MIME type registration)

Other links

 * W3C RDF page
 * Wikipedia article
 * Generating RDF from tabular data on the Web (W3C)