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The expressive power of valued constraints: hierarchies and collapses

David A. Cohen‚ Peter G. Jeavons and Stanislav Živný

Abstract

In this paper we investigate the ways in which a fixed collection of valued constraints can be combined to express other valued constraints. We show that in some cases a large class of valued constraints, of all possible arities, can be expressed by using valued constraints of a fixed finite arity. We also show that some simple classes of valued constraints, including the set of all monotonic valued constraints with finite cost values, cannot be expressed by a subset of any fixed finite arity, and hence form an infinite hierarchy.

Address
Oxford‚ UK
Institution
Computing Laboratory‚ University of Oxford
Month
April
Number
RR−07−03
Year
2007