# Constraint propagation

### From Glossary

Constraint propagation is a general term for inference techniques used in constraint programming. The basic technique consists in explicitly forbidding values or combinations of values for some variables of a problem because a given subset of its constraints cannot be satisfied otherwise. Constraint propagation appears under different names depending on both historical period and author including constraint relaxation, constraint inference, local consistency enforcing, and rule iteration.

Typically, the propagation process is repeated until a "fixed point" is reached where no further values can be removed from the domain of any variable.