RDF, short for Resource Description Framework, is a W3C endorsed technology for semantic data representation, whos proponents include Tim Berners-Lee, the inventor of hypertext. RDF is completely extensible, with every data "grammar" uniquely identified by a namespace to prevent collisions. While RDF is an abstract model capable of representing quite complex metadata structures, it can be encoded in XML for complete compatibility with XML processing tools. Many of the advantages of RDF are realized in the long term, such as built-in semantics for mapping one grammar to another for forwards compatibility.