With a growing number of Internet resources using semantic markup to give machine-readable meaning to online resources, it is often necessary to query existing semantic knowledge to fully take advantage of the information available. While SPARQL Query Language for RDF is the only  Recommendation available for this purpose, there are additional ways to query an existing knowledge base constructed from Semantic Web information listed in Reasoning and inference tools.
SPARQL Query Language for RDF
SPARQL Protocol and RDF Language The Resource Description Framework (RDF) language is widely used across the Internet to give machine-readable annotations to
- W3C's SPARQL W3C's Candidate Recommendation
- SPARQL on Wikipedia A listing of other RDF query languages
- XML.com's Introducing SPARQL A SPARQL tutorial