Strict and tolerant antidivision queries with ordinal layered preferences |
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Authors: | Patrick Bosc Olivier Pivert Olivier Soufflet |
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Affiliation: | Irisa - Enssat, University of Rennes 1, Technopole Anticipa, 22305 Lannion Cedex, France |
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Abstract: | In this paper, we are interested in taking preferences into account for a family of queries inspired by the antidivision. An antidivision query aims at retrieving the elements associated with none of the elements of a specified set of values. We suggest the introduction of preferences inside such queries with the following specificities: (i) the user gives his/her preferences in an ordinal way and (ii) the preferences apply to the divisor which is defined as a hierarchy of sets. Different uses of the hierarchy are investigated, which leads to queries conveying different semantics and the property of the result delivered is characterized. Furthermore, the case where a conjunctive stratified antidivision query returns an empty set of answers is dealt with, and an approach aimed at relaxing such queries is proposed. |
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Keywords: | Database querying Antidivision Ordinal preferences Quotient Query relaxation Fuzzy quantifiers |
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