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Combining relational algebra, SQL, constraint modelling, and local search*

Published online by Cambridge University Press:  01 January 2007

MARCO CADOLI
Affiliation:
Dipartimento di Informatica e Sistemistica, Università di Roma “La Sapienza”, Via Salaria 113, 00198 Roma, Italycadoli@dis.uniroma1.it|tmancini@dis.uniroma1.it
TONI MANCINI
Affiliation:
Dipartimento di Informatica e Sistemistica, Università di Roma “La Sapienza”, Via Salaria 113, 00198 Roma, Italycadoli@dis.uniroma1.it|tmancini@dis.uniroma1.it

Abstract

The goal of this paper is to provide a strong integration between constraint modelling and relational DBMSs. To this end we propose extensions of standard query languages such as relational algebra and SQL, by adding constraint modelling capabilities to them. In particular, we propose non-deterministic extensions of both languages, which are specially suited for combinatorial problems. Non-determinism is introduced by means of a guessing operator, which declares a set of relations to have an arbitrary extension. This new operator results in languages with higher expressive power, able to express all problems in the complexity class NP. Some syntactical restrictions which make data complexity polynomial are shown. The effectiveness of both extensions is demonstrated by means of several examples. The current implementation, written in Java using local search techniques, is described.

Type
Regular Papers
Copyright
Copyright © Cambridge University Press 2007

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