Strengthening Neighbourhood Substitution
Résumé
Domain reduction is an essential tool for solving the con-straint satisfaction problem (CSP). In the binary CSP, neighbourhoodsubstitution consists in eliminating a value if there exists another valuewhich can be substituted for it in each constraint. We show that the no-tion of neighbourhood substitution can be strengthened in two distinctways without increasing time complexity. We also show the theoreticalresult that, unlike neighbourhood substitution, finding anoptimal se-quence of these new operations is NP-hard.