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Some Algorithmic Improvments for the Containment Problem of Conjunctive Queries with Negation

Michel Leclère 1 Marie-Laure Mugnier 1 
1 GRAPHIK - Graphs for Inferences on Knowledge
LIRMM - Laboratoire d'Informatique de Robotique et de Microélectronique de Montpellier, CRISAM - Inria Sophia Antipolis - Méditerranée
Abstract : Query containment is a fundamental problem of databases. Given two queries q1 and q2, it asks whether the set of answers to q1 is included in the set of answers to q2 for any database. In this paper, we investigate this problem for conjunctive queries with negated subgoals. We use graph homomorphism as the core notion, which leads us to extend the results presented in [Ull97] and [WL03]. First, we exhibit sufficient (but not necessary) conditions for query containment based on special subgraphs of q2, which generalize that proposed in [WL03]. As a corollary, we obtain a case where the time complexity of the problem decreases. From a practical viewpoint, these properties can be exploited in algorithms, as shown in the paper. Second, we propose an algorithm based on the exploration of a space of graphs, which improves existing algorithms.
Keywords : Query Containment
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https://hal-lirmm.ccsd.cnrs.fr/lirmm-00135448
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Last modification on : Friday, August 5, 2022 - 3:03:00 PM
Long-term archiving on: : Saturday, April 16, 2022 - 6:39:40 PM

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Michel Leclère, Marie-Laure Mugnier. Some Algorithmic Improvments for the Containment Problem of Conjunctive Queries with Negation. ICDT 2007 - 11th International Conference on Database Theory, Jan 2007, Barcelona, Spain. pp.404-418, ⟨10.1007/11965893_28⟩. ⟨lirmm-00135448⟩

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