TR-2006013: The Dom Event and Its Use in Implementing Constraint Propagators

This paper argues the usefulness of the dom event in programming several constraint propagators. The dom event is introduced for implementing the AC-4 algorithm. For a binary constraint, whenever a value is excluded from the domain of a variable, the propagator with the dom event can locate the no-good values in the domain of the other variable in constant time. In this paper we present three application examples of the dom event in addition to the AC-4 algorithm for binary support constraints: the element constraint, channeling constraints, and set constraints. For each example, we show that the implementation using the dom event is significantly more efficient than previous implementations that rely on reification constraints or other techniques.