Non-binary constraints

Abstract

Since the origins of the constraint satisfaction paradigm, its restriction to binary constraints has concentrated a significant part of the work. This is understandable because new ideas/techniques are usually much simpler to present/ elaborate by first restricting them to the binary case. (See for example the arc consistency algorithms, such as AC-3 or AC-4, which have been presented first in their binary version, before being extended to non-binary constraints.) But this inclination has highly increased in the early nineties. Authors indeed justified this restriction by the fact that any non-binary constraint network can polyniomally be converted into an equivalent binary one. And, in most cases, they never extended their work to non-binary constraints.