Constraint Propagation

X = Y+1 (X,Y in 1..5)

Algorithm Change Propagation

Preprocessing generated X in 2..5, Y in 1..4

Forward checking(Node) X=3 X = 3, Y = 2

Interval consistency 5 notin X X in 2..4, Y in 1..3

Arc consistency 4 notin X X in [2,3,5], Y in [1,2,4]