SQL Nested Queries in SPARQL
One of the most powerful features of a query language is the nesting of queries, that is, the possibility of writing in a single expression a query which uses the output of other queries. SPARQL currently does not include any form of nested queries. In this paper, the authors present a proposal to incorporate nested queries into SPARQL along the design philosophy of SQL nested queries. They present rewriting algorithms and show that all the proposed nested queries can be expressed in a natural and simple extension of SPARQL syntax.