RDF and ePortfolios

Just needed to get this down before I forget... RDF & semantic web technologies generally have been nipping at the heels of several information retrieval projects for a while now. Every six months or so I check out and build the latest jena to see if we could actually build some of our IR systems using it, and it's always the same story: I start off really enthusiastically, but slowly start hitting walls that mean it's just not possible. This time around it was accessing native text and spatial indexes in my jena database backend. But.... We've been struggling for a long time now with OSPI and the SAKAI ePortfolio module and suddenly I can see an application for RDF and defined ontologies, and users being able to extend the data model in ways they want. It seems to me that jena-db could be exactly the right backend for a real usable ePortfolio system... Not sure where we'd get started building a beast like that tho.