With Topic Maps it's been solved years and years ago, and it's the part of it that the RDF world didn't think of until recently (and applied their kludges). I'm not going to bang my gong on this, just urge you to read up on PSIs.
Alex -- --------------------------------------------------------------------------- Project Wrangler, SOA, Information Alchemist, UX, RESTafarian, Topic Maps ------------------------------------------ http://shelter.nu/blog/ --------