Facebook's OpenGraph sub-classes a lot of the relationships defined in the Dublin Core vocabulary. http://opengraphprotocol.org/schema/?format=rdf http://opengr

Facebook's OpenGraph sub-classes a lot of the relationships defined in the Dublin Core vocabulary. http://opengraphprotocol.org/schema/?format=rdf http://opengraphprotocol.org/schema/?format=rdf Also, view-source a Flickr photo page. You can find some uses of RDFa and the Dublin Core vocab there.