Section: New Results

SPARQL Query Containment with ShEx Constraints

ShEx (Shape Expressions) is a language for expressing constraints on RDF graphs. In [14], we considered the problem of SPARQL query containment in the presence of ShEx constraints. We first investigated the complexity of the problem according to the fragments considered for SPARQL queries and for ShEx constraints. In particular, we showed that the complexity of SPARQL query containment remains the same with or without ShEx constraints. We developed two radically different approaches for solving the problem and we evaluated them. The first approach relies on the joint use of a ShEx validator and a tool for checking query containment without constraints. In a second approach, we showed how the problem can be solved by a reduction to a fragment of first-order logic with two variables. This alternative approach allows to take advantage of any of the many existing FOL theorem provers in this context. We evaluated how the two approaches compare experimentally, and reported on lessons learned. To the best of our knowledge, this is the first work addressing SPARQL query containment in the presence of ShEx constraints.