Rewriting Ontological Queries into Small Nonrecursive Datalog Programs

We consider the setting of ontological database access, where an A-box is given in form of a relational database D and where a Boolean conjunctive query q has to be evaluated against D modulo a T-box Σ formulated in DL-Lite or Linear Datalog±. It is well-known that (Σ, q) can be rewritten into an equivalent nonrecursive Datalog program P that can be directly evaluated over D. However, for Linear Datalog± or for DL-Lite versions that allow for role inclusion, the rewriting methods described so far result in a nonrecursive Datalog program P of size exponential in the joint size of Σ and q. This gives rise to the interesting question of whether such a rewriting necessarily needs to be of exponential size. In this paper we show that it is actually possible to translate (Σ, q) into a polynomially sized equivalent nonrecursive Datalog program P.

[1]  Alin Deutsch,et al.  The chase revisited , 2008, PODS.

[2]  Diego Calvanese,et al.  QuOnto: Querying Ontologies , 2005, AAAI.

[3]  David S. Johnson,et al.  Testing containment of conjunctive queries under functional and inclusion dependencies , 1982, J. Comput. Syst. Sci..

[4]  Diego Calvanese,et al.  Linking Data to Ontologies , 2008, J. Data Semant..

[5]  Diego Calvanese,et al.  The MASTRO system for ontology-based data access , 2011, Semantic Web.

[6]  Carsten Lutz,et al.  The Combined Approach to Query Answering in DL-Lite , 2010, KR.

[7]  Stanislav Kikot,et al.  Conjunctive Query Answering with OWL 2 QL , 2012, KR.

[8]  Boris Motik,et al.  OWL 2: The next step for OWL , 2008, J. Web Semant..

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

[10]  Giorgio Orsi,et al.  Optimizing query answering under ontological constraints , 2011, Proc. VLDB Endow..

[11]  Ronald Fagin,et al.  Data exchange: semantics and query answering , 2003, Theor. Comput. Sci..

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

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

[14]  Andrea Calì,et al.  Datalog+/-: A Family of Logical Knowledge Representation and Query Languages for New Applications , 2010, 2010 25th Annual IEEE Symposium on Logic in Computer Science.

[15]  Catriel Beeri,et al.  The Implication Problem for Data Dependencies , 1981, ICALP.

[16]  Giorgio Orsi,et al.  Semantic data markets: a flexible environment for knowledge management , 2011, CIKM '11.

[17]  Andrea Calì,et al.  Towards more expressive ontology languages: The query answering problem , 2012, Artif. Intell..

[18]  Stanislav Kikot,et al.  On (In)Tractability of OBDA with OWL 2 QL , 2011, Description Logics.

[19]  Andrea Calì,et al.  Query Answering under Non-guarded Rules in Datalog+/- , 2010, RR.

[20]  Boris Motik,et al.  Tractable query answering and rewriting under description logic constraints , 2010, J. Appl. Log..

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

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

[23]  David Maier,et al.  Testing implications of data dependencies , 1979, SIGMOD '79.

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

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

[26]  Eugene Inseok Chong,et al.  An Efficient SQL-based RDF Querying Scheme , 2005, VLDB.

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

[28]  Andrea Calì,et al.  Advanced processing for ontological queries , 2010, Proc. VLDB Endow..

[29]  Georg Gottlob,et al.  Complexity and expressive power of logic programming , 2001, CSUR.

[30]  Diego Calvanese,et al.  The DL-Lite Family and Relations , 2009, J. Artif. Intell. Res..