Constraint Propagation

Constraint propagation is an inference rule for finite domain problems that narrows the domains of variables. For instance, given the inequation

X < Y

and the basic constraints

$X \in \ensuremath{\{23,\dots,100\}}$

and

$Y \in \ensuremath{\{1,\dots,33\}}$

constraint propagation can narrow the domains of X and Y to

$X \in \ensuremath{\{23,\dots,32\}}$

and

$Y \in \ensuremath{\{24,\dots,33\}}$