2 research outputs found
Federating queries in SPARQL 1.1: syntax, semantics and evaluation
Given the sustained growth that we are experiencing in the number of SPARQL endpoints available, the need to be
able to send federated SPARQL queries across these has also grown. To address this use case, the W3C SPARQL
working group is defining a federation extension for SPARQL 1.1 which allows for combining graph patterns that can
be evaluated over several endpoints within a single query. In this paper, we describe the syntax of that extension and
formalize its semantics. Additionally, we describe how a query evaluation system can be implemented for that federation extension, describing some static optimization techniques and reusing a query engine used for data-intensive science, so as to deal with large amounts of intermediate and final results. Finally we carry out a series of experiments that show that our optimizations speed up the federated query evaluation process