. . _:vb50819225 . _:vb50819224 "Guus Schreiber" . "2004-02-10" . _:vb50819224 . _:vb50819223 . _:vb50819225 . . "OWL Web Ontology Language Reference" . _:vb50819223 . _:vb50819224 . _:vb50819225 . . . . _:vb50819223 "Mike Dean" .