Optimizing Reformulation-based Query Answering in RDF

Damian Bursztyn 1, 2 François Goasdoué 1, 3 Ioana Manolescu 1, 2 Alexandra Roatis 1, 2
1 OAK - Database optimizations and architectures for complex large data
LRI - Laboratoire de Recherche en Informatique, UP11 - Université Paris-Sud - Paris 11, Inria Saclay - Ile de France, CNRS - Centre National de la Recherche Scientifique : UMR8623
3 PILGRIM - Gradedness, Imprecision, and Mediation in Database Management Systems
IRISA-D7 - GESTION DES DONNÉES ET DE LA CONNAISSANCE
Abstract : Reformulation-based query answering is a query processing technique aiming at answering queries against data, under constraints. It consists of reformulating the query based on the constraints, so that evaluating the reformulated query directly against the data (i.e., without considering any more the constraints) produces the correct answer set.In this paper, we consider optimizing reformulation-based query answering in the setting of ontology-based data access, where SPARQL conjunctive queries are posed against RDF facts on which constraints expressed by an RDF Schema hold. The literature provides solutions for various fragments of RDF, aiming at computing the equivalent union of maximally-contained conjunctive queries w.r.t. the constraints. However, in general, such a union is large, thus it cannot be efficiently processed by a query engine.Our contribution is (i) to generalize the query reformulation language so as to investigate a space of reformulated queries (instead of having a single possible choice), and then (ii) to select the reformulated query with lower estimated evaluation cost. Our experiments show that our technique enables reformulation-based query answering where the state-of-the-art approaches are simply unfeasible, while it may decrease their costs by orders of magnitude in other cases.
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Damian Bursztyn, François Goasdoué, Ioana Manolescu, Alexandra Roatis. Optimizing Reformulation-based Query Answering in RDF. BDA'14 - Gestion de Données – Principes, Technologies et Applications, Oct 2014, Grenoble-Autrans, France. ⟨hal-01091205⟩

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