Relaxed Notions of Schema Mapping Equivalence Revisited

Recently, two relaxed notions of equivalence of schema mappings have been introduced, which provide more potential of optimizing schema mappings than logical equivalence: Data Exchange (DE) equivalence and Conjunctive Query (CQ) equivalence. In this paper, the authors systematically investigate these notions of equivalence for mappings consisting of s-t tgds and target egds and/or target tgds. They prove that both CQ- and DE-equivalence are undecidable and so are some important optimization tasks (like detecting if some dependency is redundant).

Provided by: Association for Computing Machinery Topic: Data Management Date Added: Mar 2011 Format: PDF

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