KjetilK writes "The W3C just gave SPARQL the stamp of approval. SPARQL is a query language for the Semantic Web, and differs from other query languages in that is usable across different data sources. There are already 14 implementations of the spec available. Most of them are free software. There are also billions of relations out there that are query-able, thanks to the Linking Open Data project. The structured data of Wikipedia is now query-able at DBpedia. Also, have a look at Ivan Herman's presentations on this topic."