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    Queries with negation and inequalities over lightweight ontologies

    Gutiérrez-Basulto, V. and Ibáñez-García, Y. and Kontchakov, Roman and Kostylev, E.V. (2015) Queries with negation and inequalities over lightweight ontologies. Web Semantics: Science, Services and Agents on the World Wide Web 35 (4), pp. 184-202. ISSN 1570-8268.

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    While the problem of answering positive existential queries, in particular, conjunctive queries (CQs) and unions of CQs, over description logic ontologies has been studied extensively, there have been few attempts to analyse queries with negated atoms. Our aim is to sharpen the complexity landscape of the problem of answering CQs with negation and inequalities in lightweight description logics of the DL-Lite and EL families. We begin by considering queries with safe negation and show that there is a surprisingly significant increase in the complexity from AC0 to undecidability (even if the ontology and query are fixed and only the data is regarded as input). We also investigate the problem of answering queries with inequalities and show that answering a single CQ with one inequality over DL-Lite with role inclusions is undecidable. In the light of our undecidability results, we explore syntactic restrictions to attain efficient query answering with negated atoms. In particular, we identify a novel class of local CQs with inequalities, for which query answering over DL-Lite is decidable.


    Item Type: Article
    Keyword(s) / Subject(s): Description logics, Ontological query answering. Conjunctive queries with negation, Inequalities, DL-lite, EL
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Computing and Mathematical Sciences
    Depositing User: Roman Kontchakov
    Date Deposited: 26 Nov 2015 14:04
    Last Modified: 09 Aug 2023 12:37


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