From W3C Wiki
AtomOwl is an ontology for describing rfc 2487 also know as atom. The ontology is being worked on in dev.java.net and is currently published at http://bblfish.net/work/atom-owl/2006-06-06/.
Extension for AtomOwl: http://buzzword.org.uk/rdf/atomix#. Currently just covers RFC 4685, but plan is to map various other Atom extensions to AtomOwl.