RDF/XML is a syntax, defined by the W3C, to express (i.e., serialize) an RDF graph as an XML document. RDF/XML is sometimes misidentified as simply RDF because it was introduced alongside the other W3C specifications defining RDF and was historically the first W3C official RDF serialization format. RDF/XML is the primary exchange syntax for OWL 2, and must be supported by all OWL 2 tools.
References
External links RDF/XML Syntax Specification RDF Primer RFC 3870: application/rdf+xml Media Type Registration