SPARQL Extensions

In addition to the proposed SPARQL Update specification there are a number of other proposed SPARQL Extensions.

These have been surveyed and discussed in the articles:

Dave Beckett has diagrammatically described the SPARQL 1.1 Query Execution Sequence.

References to some specific extensions are included below:

  • ARQ - Negation. Standard SPARQL can perform negation using the idiom of OPTIONAL/!BOUND. It is inconvenient and can be hard to use as complexity increases. ARQ supports additional operators for negation.In ARQ, there is the NOT EXISTS operator (UNSAID is an alias for NOT EXISTS) which acts at the point in the query where it is written.There is also an EXISTS operator.
  • ARQ - Aggregates e.g. SELECT (count(*) AS ?count) { ?s ?p ?o }