I have been visiting Stéphane Ducasse at the University Savoie in Annecy, France. A few minutes before we left for the Seaside presentation in Geneva, I had the chance to have a look at the presentation of some student projects. The most interesting project built a powerful query engine for Pier working hand-in-hand with the meta descriptions available through Magritte. The tool they present is very similar to what you have in the search of Apple Finder or the way you specify smart playlists in iTunes.
Update: A pdf version of the poster can be downloaded from posterpier.pdf.