Here's another useful RDF vocabulary: SIOC, Semantically-Interlinked Online Communities:

SIOC (Semantically Interlinked Online Communities) is an ontology for describing discussion forums and posts on topic threads in online community sites. This includes but is not limited to: blogs, bulletin boards, mailing lists, newsgroups, etc.

My major issue with SIOC is that it's working in the same knowledge space as Atom N3 (previously mentioned here) but uses a different vocabulary. Obviously, RDF knows how to work around this but it's a shame that SIOC didn't use Atom's painstakingly thought out terminology. I suspect this happened because SIOC comes more from the Bulletin Board world than the Blogging one.

One of the key concepts for the BlogMatrix platform is that we should be able to produce RDF output backing all pages of the site. To do this, we need to have a RDF vocabularies to describe the encoded data and of course the best way to do this is to reuse existing ones. Here's a couple:

• FOAF - persons, projects, organizations, groups, documents, images and online groups
• GEO - lat, lon, WGS84
• RDFizers - tools for converting existing data types into RDF (to be mined for information)

Idea: we really need to make the Link extension handle multiple links per post.