Domain Filtering Consistencies

TL;DR

This paper reviews and compares recent local consistency techniques in constraint reasoning that strengthen arc consistency without altering the network structure, analyzing their theoretical properties and practical performance.

Contribution

It provides a comprehensive overview and comparison of new local consistency methods that improve pruning efficiency without changing the constraint graph structure.

Findings

Stronger local consistencies can be more effective in pruning than arc consistency.

Experimental results show varying trade-offs between pruning power and enforcement time.

Relations between different local consistencies are clarified.

Abstract

Enforcing local consistencies is one of the main features of constraint reasoning. Which level of local consistency should be used when searching for solutions in a constraint network is a basic question. Arc consistency and partial forms of arc consistency have been widely studied, and have been known for sometime through the forward checking or the MAC search algorithms. Until recently, stronger forms of local consistency remained limited to those that change the structure of the constraint graph, and thus, could not be used in practice, especially on large networks. This paper focuses on the local consistencies that are stronger than arc consistency, without changing the structure of the network, i.e., only removing inconsistent values from the domains. In the last five years, several such local consistencies have been proposed by us or by others. We make an overview of all of them, and highlight some relations between them. We compare them both theoretically and experimentally, considering their pruning efficiency and the time required to enforce them.