In the December 17th cnn.com/technology article Making sense of the ‘semantic Web’, Steve Mollman wrote:

I’ve been looking for a SPARQL endpoint that provides new data fairly regularly—not just new triples to query, but data that is new to the world, such as from a stock ticker feed. If the RDFa on digg.com pages was accumulated in a database that could be queried as a SPARQL endpoint, that would certainly qualify, and it would be fun to play with.

The open-source program Pellet is described as an OWL reasoner, but I’ve used it mostly as a SPARQL engine that happens to understand OWL. So, for example, if I have RDF that says “Loretta’s spouse is Leroy and spouse is a symmetric property,” but the data makes no mention of Leroy’s spouse, and I ask Pellet “who is Leroy’s spouse,” it can give me the answer.

In the first project I did with SPARQL, D2RQ, and MySQL I used D2RQ to pull all the relational data into a disk file and then queried that after adding some OWL-based metadata. D2RQ does let you execute SPARQL queries against a live relational database, instead of dumping data to a file and querying that, so I wanted to see the effects for myself. This would work better as a live demo, but you could think of it as a script for one.

Last week I mentioned that the Linked Movie Database SPARQL endpoint would be fun to play with, and it has been. I used my spreadsheetSPARQL interface to send the following queries to their http://sparql.linkedmdb.org:2020/linkedmdb SPARQL endpoint.

In an earlier project I did querying relational data with SPARQL, I wanted to demonstrate how adding OWL metadata made it possible to answer useful queries that couldn’t have been answered with just the original data. I did this using two simple databases of one table each, but recently, while helping someone who was also using the D2RQ interface to provide access to some relational data, I decided to get more comfortable with using SPARQL to query data from multi-table relational…