Can I include subqueries in a SPARQL query?
While SPARQL does support nested graph patterns, it does not directly support subqueries (for example, the FROM clause of a SPARQL query cannot itself contain a CONSTRUCT query which generates the dataset to be queried against). The Data Access Working Group postponed this issue in early 2005. A very limited form of subqueries can be accomplished with SPARQL engines that will perform HTTP GETs upon graphs named in FROM or FROM NAMED clauses by creating a URL consisting of an embedded SPARQL CONSTRUCT query submitted to a SPARQL endpoint and supplying this URL as part of the RDF dataset being queried. In practice, this technique is often inefficient and is subject to possible URL-maximum-length restrictions of the involved software.
