SIOC

http://drupal.org/project/vcard

Suggested simplification of the syntax, and a small correction, from <a href="http://lists.w3.org/Archives/Public/public-rdf-in-xhtml-tf/2008Oct/0026.html"

So the way I see this working for Taxonomy module is that a the URI for a publicly defined, shared ontology can be added to a Drupal term as metadata, which the proposed taxonomy_term_load hook would enable.