Proceedings of the Twenty-Third International Joint Conference on Artificial Intelligence Compact Rewritings for Existential Rules ∗

Querying large databases while taking ontologies into account is currently a very active domain research. In this paper, we consider ontologies described by existential rules (also known as Datalog+/-), a framework that generalizes lightweight description logics. A common approach is to rewrite a conjunctive query w.r.t an ontology into a union of conjunctive queries (UCQ) which can be directly evaluated against a database. However, the practicability of this approach is questionable due to 1) the weak expressivity of classes for which efficient rewriters have been implemented 2) the large size of optimal rewritings using UCQ. We propose to use semi-conjunctive queries (SCQ), which are a restricted form of positive existential formulas, and compute sound and complete rewritings, which are union of SCQ (USCQ). A novel algorithm for query rewriting, COMPACT, is presented. It computes sound and complete rewritings for large classes of ontologies. First experiments show that USCQ are both efficiently computable and more efficiently evaluable than their equivalent UCQ.

[1]  Diego Calvanese,et al.  High Performance Query Answering over DL-Lite Ontologies , 2012, KR.

[2]  Jean-François Baget,et al.  On rules with existential variables: Walking the decidability line , 2011, Artif. Intell..

[3]  Diego Calvanese,et al.  Tractable Reasoning and Efficient Query Answering in Description Logics: The DL-Lite Family , 2007, Journal of Automated Reasoning.

[4]  Boris Motik,et al.  Efficient Query Answering for OWL 2 , 2009, SEMWEB.

[5]  Giorgos B. Stamou,et al.  Optimized Query Rewriting for OWL 2 QL , 2011, CADE.

[6]  Marie-Laure Mugnier,et al.  Sound and Complete Forward and backward Chainingd of Graph Rules , 1996, ICCS.

[7]  Diego Calvanese,et al.  The Description Logic Handbook , 2007 .

[8]  Diego Calvanese,et al.  The Description Logic Handbook: Theory, Implementation, and Applications , 2003, Description Logic Handbook.

[9]  Riccardo Rosati,et al.  Improving Query Answering over DL-Lite Ontologies , 2010, KR.

[10]  Sebastian Rudolph,et al.  A Generic Querying Algorithm for Greedy Sets of Existential Rules , 2012, KR.

[11]  Carsten Lutz,et al.  The Combined Approach to Ontology-Based Data Access , 2011, IJCAI.

[12]  Michaël Thomazo,et al.  A Sound and Complete Backward Chaining Algorithm for Existential Rules , 2012, RR.

[13]  Thomas Schwentick,et al.  Rewriting Ontological Queries into Small Nonrecursive Datalog Programs , 2011, Description Logics.

[14]  Giorgio Orsi,et al.  Ontological queries: Rewriting and optimization , 2011, 2011 IEEE 27th International Conference on Data Engineering.

[15]  Andrea Calì,et al.  A general datalog-based framework for tractable query answering over ontologies , 2009, SEBD.

[16]  Boris Motik,et al.  Small Datalog Query Rewritings for EL , 2012, Description Logics.

[17]  Franz Baader,et al.  How Pervasive Is the Myerson-Satterthwaite Impossibility? , 2009, IJCAI.

[18]  Giorgos Stoilos,et al.  Incremental Query Rewriting for OWL 2 QL , 2012, Description Logics.

[19]  Andrea Calì,et al.  A general Datalog-based framework for tractable query answering over ontologies , 2012, J. Web Semant..

[20]  Andrea Calì,et al.  Query Rewriting under Non-Guarded Rules , 2010, AMW.

[21]  Carsten Lutz,et al.  The Combined Approach to OBDA: Taming Role Hierarchies using Filters , 2012, SSWS+HPCSW@ISWC.

[22]  Giorgos Stoilos,et al.  Benchmarking Ontology-Based Query Rewriting Systems , 2012, AAAI.

[23]  Andrea Calì,et al.  Taming the Infinite Chase: Query Answering under Expressive Relational Constraints , 2008, Description Logics.