A Query and Inference Service for RDF

The creation of RDF raises the prospect of a widely accepted standard for representing expressive declarative knowledge on the Web. However, just representing knowledge and information is not enough: users as well as information agents have to query and use the data in several ways. An RDF Query specification would allow a range of applications to exploit any information source which can be represented in terms of the RDF data model.

http://www.w3.org/TandS/QL/QL98/pp/queryservice.html