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Complexity of Clausal Constraints Over Chains

Nadia CreignouContact Information, Miki HermannContact Information, Andrei KrokhinContact Information and Gernot SalzerContact Information

(1)  LIF (CNRS, UMR 6166), Univ. de la Méditerranée, 13288 Marseille cedex 9, France
(2)  LIX (CNRS, UMR 7161), École Polytechnique, 91128 Palaiseau cedex, France
(3)  Department of Computer Science, University of Durham, Durham, DH1 3LE, UK
(4)  Technische Universität Wien, Favoritenstraße 9-11, 1040 Vienna, Austria

Published online: 28 September 2007

Abstract   We investigate the complexity of the satisfiability problem of constraints over finite totally ordered domains. In our context, a clausal constraint is a disjunction of inequalities of the form xd and xd. We classify the complexity of constraints based on clausal patterns. A pattern abstracts away from variables and contains only information about the domain elements and the type of inequalities occurring in a constraint. Every finite set of patterns gives rise to a (clausal) constraint satisfaction problem in which all constraints in instances must have an allowed pattern. We prove that every such problem is either polynomially decidable or NP-complete, and give a polynomial-time algorithm for recognizing the tractable cases. Some of these tractable cases are new and have not been previously identified in the literature.

Keywords  Constraint satisfaction problems - Complexity - Finite totally ordered domains - Inequalities - Clausal patterns - Dichotomy theorem

The work has been supported by ÉGIDE 06606ZF, ÖAD Amadeus 18/2004, and by UK EPSRC grants EP/C543831/1 and EP/C54384X/1.

Contact Information Nadia Creignou
Email: Nadia.Creignou@lif.univ-mrs.fr

Contact Information Miki Hermann (Corresponding author)
Email: Miki.Hermann@lix.polytechnique.fr

Contact Information Andrei Krokhin
Email: Andrei.Krokhin@durham.ac.uk

Contact Information Gernot Salzer
Email: salzer@logic.at
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Referenced by
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  1. Jonsson, Peter (2008) Approximability of Clausal Constraints. Theory of Computing Systems
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