At the Billion Triples Challenge this afternoon Cathrin Weiss showed off i-MoCo. It's a demonstration not only of a Semantic Web application with an iPhone using a stupid number of triples, but also of their indexing technique Hexastore which does all 6 indexes of RDF's subject, predicate and object in order to improve querying (they are ordered which allows you to do merge sorts). Actually, this made me think that the next steps in RDF triple stores will be indexes that are optimised for SPARQL operations and OWL inferences. Indexes for transitive closure perhaps? The data is regular and the storage is available to index triples that improve querying performance.
That wasn't the only impressive demo today. For me it's a toss up between another iPhone SemWeb demo, DBPedia mobile and SemaPlorer. DBPedia stood out because it was the only one that allowed you to write data to the Semantic Web rather than just read the carefully prepared triples. For a similar reason I thought SemaPlorer was good because they tried to do more by making it more generic like integrating flickr. But they were all excellent, all of them showing what you get with a billion or more triples and inferencing.
That combined with the guys at Freebase making all of their data available as RDF and it was a big day for the Semantic Web.
Update: I noticed that John Giannadrea's talk when he mentioned the three aspects to Freebase he went from the bottom up - probably reading too much into it.
Update: Also caught an interview with John Francis the guy who stopped talking, started walking, stopped taking mechanical transport and tried to change the world.
Update: ISWC 2008 awards have been published.