This paper introduces SKOS Core, an RDF vocabulary for expressing the basic structure and content of concept schemes (thesauri, classification schemes, subject heading lists, taxonomies, terminologies, glossaries and other types of controlled vocabulary).  SKOS Core is published and maintained by the W3C Semantic Web Best Practices and Deployment Working Group.  The main purpose of this paper is to provide an initial basis for establishing clear recommendations for the use of SKOS Core and DCMI Metadata Terms in combination.  Also discussed are management policies for SKOS Core and other RDF vocabularies, and the relationship between a “SKOS concept scheme” and an “RDFS/OWL Ontology”.