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Scalar aggregation in inconsistent databases

✍ Scribed by Marcelo Arenas; Leopoldo Bertossi; Jan Chomicki; Xin He; Vijay Raghavan; Jeremy Spinrad

Publisher
Elsevier Science
Year
2003
Tongue
English
Weight
260 KB
Volume
296
Category
Article
ISSN
0304-3975

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✦ Synopsis

We consider here scalar aggregation queries in databases that may violate a given set of functional dependencies. We deΓΏne consistent answers to such queries to be greatest-lowest/leastupper bounds on the value of the scalar function across all (minimal) repairs of the database. We show how to compute such answers. We provide a complete characterization of the computational complexity of this problem. We also show how tractability can be improved in several special cases (one involves a novel application of Boyce-Codd Normal Form) and present a practical hybrid query evaluation method.

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We propose a semantics for aggregates in deductive databases based on a notion of minimality. Unlike some previous approaches, we form a minimal model of a program component including aggregate operators, rather than insisting that the aggregate apply to atoms that have been fully determined or that