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    Games for query inseparability of description logic knowledge bases

    Botoeva, E. and Kontchakov, Roman and Ryzhikov, Vladislav and Wolter, F. and Zakharyaschev, Michael (2016) Games for query inseparability of description logic knowledge bases. Artificial Intelligence 234 , pp. 78-119. ISSN 0004-3702.

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    We consider conjunctive query inseparability of description logic knowledge bases with respect to a given signature---a fundamental problem in knowledge base versioning, module extraction, forgetting and knowledge exchange. We give a uniform game-theoretic characterisation of knowledge base conjunctive query inseparability and develop worst-case optimal decision algorithms for fragments of Horn-ALCHI, including the description logics underpinning OWL 2 QL and OWL 2 EL. We also determine the data and combined complexity of deciding query inseparability. While query inseparability for all of these logics is P-complete for data complexity, the combined complexity ranges from P- to ExpTime- to 2ExpTime-completeness. We use these results to resolve two major open problems for OWL 2 QL by showing that TBox query inseparability and the membership problem for universal conjunctive query solutions in knowledge exchange are both ExpTime-complete for combined complexity. Finally, we introduce a more flexible notion of inseparability which compares answers to conjunctive queries in a given signature over a given set of individuals. In this case, checking query inseparability becomes NP-complete for data complexity, but the ExpTime- and 2ExpTime-completeness combined complexity results are preserved.


    Item Type: Article
    Keyword(s) / Subject(s): Description logic, Knowledge base, Conjunctive query, Query inseparability, Games on graphs, Computational complexity
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Computing and Mathematical Sciences
    Depositing User: Roman Kontchakov
    Date Deposited: 11 Feb 2016 11:13
    Last Modified: 09 Aug 2023 12:37


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