A System for Tractable Computation of Negative Answers to Conjunctive Queries
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Users of conjunctive query answering (CQA) in description logic (DL) ontologies may often confront a problem that there are insufficiently many or even no certain answers to a given conjunctive query (CQ). It is needed to suggest users negative answers to a given CQ that are expected to be in the result but actually do not occur there while explaining why these answers are not certain ones. To this end, we develop a system which incrementally computes negative answers in a user interactive mode for a given CQ and a given consistent DL ontology. A negative answer that is incrementally computed in level \(k\) is a tuple such that there is a set of \(k\) assertions whose appending to the ontology makes this tuple a certain answer while keeping the ontology consistent. The proposed computational method works in polynomial time in terms of data complexity for DL ontologies with first-order rewritable TBoxes.
KeywordsConjunctive Queries (CQ) User Interaction Module Conjunctive Query Answering (CQA) Lehigh University Benchmark (LUBM) OBDA Systems
This work is partly supported by the NSFC grants (61375056 and 61005043), the Guangdong Natural Science Foundation (S2013010012928), the Undergraduate Innovative Experiment Projects in Guangdong University of Foreign Studies (1184613038, 1184613026 and 201411846043), and the Business Intelligence Key Team of Guangdong University of Foreign Studies (TD1202).
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