RDFS or RDF Schema is an extensible knowledge representation language, providing basic elements for the description of ontologies, otherwise called RDF vocabularies, intended to structure RDF resources. The http://www.w3.org/TR/1998/WD-rdf-schema-19980409/ first version was published by W3C in April 1998, and the http://www.w3.org/TR/rdf-schema/ final W3 C recommendation was released in February 2004. Main RDFS components are included in the more expressive language OWL.