Reformulating Positive Table Constraints Using Functional Dependencies

  • Authors:
  • Hadrien Cambazard;Barry O'Sullivan

  • Affiliations:
  • Cork Constraint Computation Centre Department of Computer Science, University College Cork, Ireland;Cork Constraint Computation Centre Department of Computer Science, University College Cork, Ireland

  • Venue:
  • CP '08 Proceedings of the 14th international conference on Principles and Practice of Constraint Programming
  • Year:
  • 2008

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Abstract

Constraints that are defined by tables of allowed tuples of assignments are common in constraint programming. In this paper we present an approach to reformulating table constraints of large arity into a conjunction of lower arity constraints. Our approach exploits functional dependencies. We study the complexity of finding reformulations that either minimize the memory size or arity of a constraint using a set of its functional dependencies. We also present an algorithm to compute such reformulations. We show that our technique is complementary to existing approaches for compressing extensional constraints.