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A Constraint Directed Model for Partial Constraint Satisfaction Problems

  • Sivakumar Nagarajan
  • Scott Goodwin
  • Abdul Sattar
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1822)

Abstract

For many constraint satisfaction problems, finding complete solutions is impossible (i.e. problems may be over-constrained). In such cases, we want a partial solution that satisfies as many constraints as possible. Several backtracking and local search algorithms exist that are based on the assignment of values to variables in a fixed order, until a complete solution or a reasonably good partial solution is obtained. In this study, we examine the dual graph approach for solving CSPs. The idea of dual graphs can be naturally extended to another structure-driven approach to CSPs, constraint directed backtracking that inherently handles k-ary constraints. In this paper, we present a constraint directed branch and bound (CDBB) algorithm to address the problem of over-constrained-ness. The algorithm constructs solutions of higher arity by joining solutions of lower arity. When computational resources are bounded, the algorithm can return partial solutions in an anytime fashion. Some interesting characteristics of the proposed algorithm are discussed. The algorithm is implemented and tested on a set of randomly generated problems. Our experimental results demonstrate that the CDBB consistently finds better solutions more quickly than backtracking with branch and bound. Our algorithm can be extended with intelligent backtracking schemes and local consistency maintenance mechanisms just like backtracking has been in the past.

Keywords

Search Tree Constraint Satisfaction Constraint Satisfaction Problem Local Search Algorithm Dual Graph 
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 2000

Authors and Affiliations

  • Sivakumar Nagarajan
    • 1
  • Scott Goodwin
    • 1
  • Abdul Sattar
    • 2
  1. 1.Department of Computer ScienceUniversity of ReginaReginaCanada
  2. 2.School of Computing and Information TechnologyGriffith UniversityNathanAustralia

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