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Implication and Referential Constraints: A New Formal Reasoning (1994)
| Citations: | 28 - 1 self |
BibTeX
@MISC{Zhang94implicationand,
author = {Xubo Zhang and Z. Meral Ozsoyoglu},
title = {Implication and Referential Constraints: A New Formal Reasoning},
year = {1994}
}
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Abstract
In this paper, we address the issue of reasoning with two classes of commonly used semantic integrity constraints in database and knowledge-base systems: implication constraints and referential constraints. We first consider a central problem in this respect, the IRC-refuting problem, which is to decide whether a conjunctive query always produces an empty relation on (finite) database instances satisfying a given set of implication and referential constraints. Since the general problem is undecidable, we only consider acyclic referential constraints. Under this assumption, we prove that the IRC--refuting problem is decidable, and give a novel necessary and sufficient condition for it. Under the same assumption, we also study several other problems encountered in semantic query optimization, such as the semantics-based query containment problem, redundant join problem, and redundant selection-condition problem, and show that they are polynomially equivalent or reducible to the IRC-refuting problem. Moreover, we give results on reducing the complexity for some special cases of the IRC-refuting problem.
Keyphrases
referential constraint new formal reasoning irc-refuting problem acyclic referential constraint central problem sufficient condition database instance semantics-based query containment problem several problem semantic integrity constraint conjunctive query redundant selection-condition problem implication constraint irc refuting problem empty relation semantic query optimization special case knowledge-base system general problem join problem
