Constraint Propagation Example Graph Coloring R G. B Different-color constraint Initial Domains Arc examined Value deleted R, B none V1(G) R G G V2>V2 Arcs to examine V<Vo,V>V Delete unmentioned tail values F An element of a variable 's domain is removed THEN add all arcs to that variable to the examination queue Constraint Propagation Example RG Graph coloring xgtDifferent-color constraint ( R,66 Arc examined value deleted R, B V>V V2(G) Arcs to examine V2<V3V2>V1 Delete unmentioned tail values IF An element of a variables domain is removed THEN add all arcs to that variable to the examination qu19 Constraint Propagation Example R,G,B R, G G Different-color constraint V1 V2 V3 V2 >V3 V1 V (G) 1-V3 V1 – V2 none Arc examined Value deleted Graph Coloring Initial Domains R, B R, G G V2 V3 V1 Arcs to examine V2<V3, V2>V1 • Delete unmentioned tail values IF An element of a variable’s domain is removed, THEN add all arcs to that variable to the examination queue. 20 Constraint Propagation Example R,G,B R, G G Different-color constraint V1 V2 V3 V2 V (G) 2 >V3 V1 V (G) 1-V3 V1 – V2 none Arc examined Value deleted Graph Coloring Initial Domains R, B R, G G V2 V3 V1 Arcs to examine V2<V3, V2>V1 • Delete unmentioned tail values IF An element of a variable’s domain is removed, THEN add all arcs to that variable to the examination queue