Departmental Papers (CIS)

Document Type

Journal Article

Date of this Version

2006

Comments

doi>10.1145/1121995.1122010

Alin Deutsch, Lucian Popa, Val Tannen: Query reformulation with constraints. SIGMOD Record 35(1): 65-73 (2006)

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Abstract

Let Σ1, Σ2 be two schemas, which may overlap, C be a set of constraints on the joint schema Σ1 ∪ Σ2, and q1 be a Σ1-query. An (equivalent) reformulation of q1 in the presence of C is a Σ2-query, q2, such that q2 gives the same answers as q1 on any Σ1 ∪ Σ2-database instance that satisfies C. In general, there may exist multiple such reformulations and choosing among them may require, for example, a cost model.

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Date Posted: 24 July 2012