You may have seen the recent news about an RDF breakthrough (this even hit non-tech media). Well, the paper is here and is worth a read. It's not actually a terribly well written paper and you'll need to read the paper on the index structure to get what's going on.
Personally, I would have broadcast the requests to all the index servers because hashing to buckets makes resizing the number of buckets very hard. Also, I'm not sure about their data flow for joining sets. But that's fairly minor.
If you liked those, try the paper on ranking too.
Of course, this begs the question of how RDF will ever be useful for anything - because it isn't at the moment and it's been around a while. I'm not going into that now.
(and, if you needed any more reason to switch to Xmonad from ion, see these recent comments from the author)