The SIOC vocabulary is based on RDF and is defined using RDFS. SIOC documents may use other existing ontologies to enrich the information described. Additional information about the creator of the post can be described using FOAF Vocabulary and the foaf:maker property. Rich content of the post (e.g., an HTML representation) can be described using AtomOWL or RSS 1.0 Content module. The SIOC project was started in 2004 by John G. Breslin and Uldis Bojars at DERI, NUI Galway. In 2007, SIOC became a W3C Member Submission.