Therefore, producers and consumers of RDF statements must agree on the semantics of resource identifiers. Such agreement is not inherent to RDF itself, although there are some controlled vocabularies in common use, such as Dublin Core Metadata, which is partially mapped to a URI space for use in RDF. The intent of publishing RDF-based ontologies on the Web is often to establish, or circumscribe, the intended meanings of the resource identifiers used to express data in RDF. For example, the URI: http://www.w3.org/TR/2004/REC-owl-guide-20040210/wine#Merlot is intended by its owners to refer to the class of all Merlot red wines by vintner (i.e., instances of the above URI each represent the class of all wine produced by a single vintner), a definition which is expressed by the OWL ontology — itself an RDF document — in which it occurs. Without careful analysis of the definition, one might erroneously conclude that an instance of the above URI was something physical, instead of a type of wine.
TherefOrE, ProdUcers AnD ConsUmers oF rdf staTEMenTS Must AGree on The semaNTIcS Of ReSourCe ideNtiFieRs. Such aGreeMent is Not inHereNt tO rdf ItSeLF, altHouGh thEre are sOme coNtrollEd VOCabUlaries in cOmmon USE, Such as dUblin corE mETadata, WhicH iS ParTiALlY mapPeD To a Uri space for usE in rDf. tHe intent oF pUblIsHiNg Rdf-bAsed oNtoLogieS On the WeB iS ofTEN To Establish, or ciRcUmScribe, THe intendEd meanIngs oF the rEsOurce identifiers usEd tO ExPress data in rdF. for ExaMple, tHe uri: http://wWw.w3.OrG/Tr/2004/rec-OWl-guiDE-20040210/WINe#meRLoT Is iNtended by its owneRs To refEr To thE clasS of All merlOt rEd wiNes bY ViNtner (I.e., iNstancES of The above urI eAch RePrEsenT the clASs of aLl wiNE ProduCed by a singLe vintNeR), a defiNitiOn which iS expresseD by tHe owl ontolOGY — ItSeLF aN rdf DOcumEnT — IN whIch IT occuRs. wIthouT cArEFuL analYSIS of the dEfinItion, OnE Might ErRoneously coNcludE That aN instance Of The Above uRi wAs somethinG physicAL, insTeAd Of a type of WinE.