Characterizing certain answers via compactness

Abstract : In relational data integration, some approaches rely on logic programming to get answers for one query from several sources. More precisely, in the mediation setting where a virtual global schema linked to all local source schemas is assumed, some algorithms are based on SLD-resolution to generate rewritings of a query expressed on the global schema, so that it can be evaluated on the many sources. The aim of this evaluation is to obtain the certain answers [1]. These answers are the answers that are always obtained when a user evaluates his query on any materialization of the global schema which reflects the source data [9]. Of course, it has been shown that the generated rewritings, especially via SLD-resolution, could compute the certain answers. However, from a more general point of view, and up to our knowledge, no certain answers characterization w.r.t. answers of a definite program formalizing a mediation setting has been proposed yet. This is the main contribution of this paper, which is based on a new compactness result that characterizes certain answers w.r.t. an extension to infinite models of certain answers.
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https://hal.archives-ouvertes.fr/hal-02062406
Contributor : Christophe Rey <>
Submitted on : Monday, April 1, 2019 - 2:59:28 PM
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Christophe Rey, Elias Tahhan-Bittar, Jerzy Tomasik. Characterizing certain answers via compactness. 2019. ⟨hal-02062406⟩

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