Kendall Clark - SPARQL: Web 2.0 Meet the Semantic Web:

"RDF is pretty foundational to the Semantic Web, and it's got a data model, a formal semantics, and a concrete serialization (in XML). What it didn't have till lately was a standard query language. Imagine relational algebra and RDBMSes without SQL. Pretty hard to imagine. So the SemWeb needed a SQL. It stood up the Data Access Working Group, which has been working for about 20 months and has come up with SPARQL - an RDF query language and protocol."