I’ve known for a while about ways to dig into the vocabularies used in DBpedia’s massive collection of triples, and I’ve used terms from these vocabularies to query for information such as Bart Simpson blackboard messages and US presidents’ ages at inauguration. I saw these terms as “field” names to use when querying this body of data.

Since I first wrote on sending DBpedia SPARQL queries about Bart’s blackboard messages at the start of Simpsons episodes, I’ve learned a lot more about SPARQL (reading the spec helped) and I wanted to walk through some of the things I’ve learned by expanding on and refining my original query.

In an August 19th interview with Jon Udell, David Huynh of Freebase (and formerly of MIT’s Project Simile) introduced his Freebase demo by describing a hypothetical query to a database asking for presidents’ ages when they are inaugurated and whether there’s a trend that we’re getting younger presidents. Jon replies: