Half Reification and Flattening

  • Thibaut Feydy
  • Zoltan Somogyi
  • Peter J. Stuckey
Part of the Lecture Notes in Computer Science book series (LNCS, volume 6876)

Abstract

Usually propagation-based constraint solvers construct a constraint network as a conjunction of constraints. They provide propagators for each form of constraint c. In order to increase expressiveness, systems also usually provide propagators for reified forms of constraints. A reified constraint b ↔ c associates a truth value b with a constraint c. With reified propagators, systems can express complex combinations of constraints using disjunction, implication and negation by flattening. In this paper we argue that reified constraints should be replaced by half-reified constraints of the form b → c. Half-reified constraints do not impose any extra burden on the implementers of propagators compared to unreified constraints, they can implement reified propagators without loss of propagation strength (assuming c is negatable), they extend automatically to global constraints, they simplify the handling of partial functions, and can allow flattening to give better propagation behavior.

Keywords

Relational Semantic Boolean Variable Global Constraint Complex Constraint Resource Constrain Project Schedule Problem 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Thibaut Feydy
    • 1
  • Zoltan Somogyi
    • 1
  • Peter J. Stuckey
    • 1
  1. 1.National ICT Australia and the University of MelbourneAustralia

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