منابع مشابه
Safe Query Languages for Constraint DatabasesPeter
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Motivated by constraint complex values which allow us to represent nested finitely representable sets, we study the expressive power of various query languages over constraint complex value databases. The tools we use come in the form of collapse results which are well established results in the context of first-order logic. We show that activegeneric collapse carries over to second-order logic...
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We study the structure of rst-order and second-order queries over constraint databases. Constraint databases are formally modeled as nite relational structures embedded in some xed innnite structure. We concentrate on problems of elimination of constraints , reducing quantiication range to the active domain of the database and obtaining new complexity bounds. We show that for a large class of s...
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We investigate the problem of how to extend constraint query languages with aggregate operators. We deal with standard relational aggregation, and also with aggregates speciic to spatial data, such as volume. We study several approaches, including the addition of a new class of approximate aggregate operators which allow an error tolerance in the computation. We show how techniques based on VC-...
متن کاملLinear Constraint Query Languages: Expressive Power and Complexity
We give an AC upper bound on the complexity of rst-oder queries over (in nite) databases de ned by restricted linear constraints. This result enables us to deduce the non-expressibility of various usual queries, such as the parity of the cardinality of a set or the connectivity of a graph in rst-order logic with linear constraints.
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ژورنال
عنوان ژورنال: Journal of Computer and System Sciences
سال: 1995
ISSN: 0022-0000
DOI: 10.1006/jcss.1995.1051