Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532003
Title: Tractable query answering for description logics via query rewriting
Author: Perez-Urbina, Hector M.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2010
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Abstract:
We consider the problem of answering conjunctive queries over description logic knowledge bases via query rewriting. Given a conjunctive query Q and a TBox T, we compute a new query Q′ that incorporates the semantic consequences of T such that, for any ABox A, evaluating Q over T and A can be done by evaluating the new query Q′ over A alone. We present RQR—a novel resolution-based rewriting algorithm for the description logic ELHIO¬ that generalizes and extends existing approaches. RQR not only handles a spectrum of logics ranging from DL-Lite_core up to ELHIO¬, but it is worst-case optimal with respect to data complexity for all of these logics; moreover, given the form of the rewritten queries, their evaluation can be delegated to off-the-shelf (deductive) database systems. We use RQR to derive the novel complexity results that conjunctive query answering for ELHIO¬ and DL-Lite+ are, respectively, PTime and NLogSpace complete with respect to data complexity. In order to show the practicality of our approach, we present the results of an empirical evaluation. Our evaluation suggests that RQR, enhanced with various straightforward optimizations, can be successfully used in conjunction with a (deductive) database system in order to answer queries over knowledge bases in practice. Moreover, in spite of being a more general procedure, RQR will often produce significantly smaller rewritings than the standard query rewriting algorithm for the DL-Lite family of logics.
Supervisor: Horrocks, Ian ; Motik, Boris Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.532003  DOI: Not available
Keywords: Applications and algorithms ; Computing ; Modal logic ; Theory and automated verification ; Description Logics ; Query Answering ; Query Rewriting
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