PUBLIC MARKS with tags SPARQL & specification

The growing suite of SPARQL query services offer consumers an opportunity to merge data distributed across the web. A small number of extensions to SPARQL 1.1 enable expression of the merging queries. In particular, a SERVICE allows one to direct a portion of a query to a particular SPARQL query service, just as a GRAPH directs queries to particular named graphs. A BINDINGS keyword adds a compact syntax for tranfering results which constrain a query. The combination of these extensions allows one to compose a query which delegates parts of the query to a series of services. This specification defines the syntax and semantics of these extensions.