GLad you posted this here Benjamin (I'm the ben that just tweeted you re: PESO)!
It is a few levels deeper than ProM has been able to dig so far, but brings some interesting approaches to the algorithm(s). More and more the question becomes (meta)data entry, storage, linking...or else smart tools for scraping...or both.
I'm a believer right now in some kind of hybrid categorical framework that blends a conventional taxonomy with emergent growth/refinement and extensibility (folksonomy) -- maybe 'faxonomy' ?? to find some common handles and relations for data types/entities (and/or translation engine). A while ago i had quite an 'aha' when the old-fashioned 5(6) W questions jumped forward as great primary dimensions-- who, what, when, where, why, how...that will make sense for all types of users and interfaces, while offering good specificity and continuity.
So yes, user-submitted (or use-defined) metadata that is site-independent, yet somehow cumulative...Fabio Barone (on this list, and I think you know him too) just reminded me of microformats as a bridge between rigid semantic systems and open organic web development. Perhaps we standardize a few of these, but would still imply central indexing service...and also a subjective trust component I think.
Probably getting close to Tav's
togethr.at /espian/ampify systemology now. But I want to point out also that this kind of 'grail quest' tends to range out quite a long ways from the mainstream action and even if there is feedback effect from the adventurous scouts, there is probably much greater effect by trying to stay well within reach of the 'multitudes' and even actively 'marketing' products/services with narrower, stylish, focus.
I may be one of the few left here who still supports the 'dating site' analogy as a core theme for project matching, but that's the main reason: it's a familiar, exhilarating, buzzworthy bridge to bring a lot of people over on.
Anyhow, good thinking (all 24 years worth ; ) and hope this feeds into the discussion. I'll share more about PESO soon (almost time to beg for money to make it happen).