so in some sense you can look at tagging as a core operation - if you want a quick hack solution, restrict the vocabulary that you are allowing for tagging s.t.

so in some sense you can look at tagging as a core operation - if you want a quick hack solution, restrict the vocabulary that you are allowing for tagging s.t. each unique term is an instance in some ontology, this allows you to build subsumption hierarchies etc. I'd just read the regular RDF on rdfabout.com and understand that really, deeply then define a namespace that is like http://yoursite/tags http://yoursite/tags and then write an OWL or RDFS ontology in Protege, which is free and open source and evolved into a tool I worked on for a different company and they have a free version called topbraid composer. I'd highly recommend you move off of the microformat/RDFa solution and hack in your first draft using simple tags that you then describe in an ontology. Referential semantics is actually complicated so don't get discouraged and work up incrementally.