Constraint Propagation Example Graph Coloring R G. B Different-color constraint Initial Domains Arc examined Value deleted R, B none V,G) R G V3>V2 none Arcs to examine 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 V2(G) V>v Arcs to examine Delete unmentioned tail values IF An element of a variables domain is removed THEN add all arcs to that variable to the examination qu23 Constraint Propagation Example R,G,B R, G G Different-color constraint V1 V2 V3 V3 > V2 none 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 V2 V3 V1 Arcs to examine V2>V1 , V1>V2 • 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. 24 Constraint Propagation Example R,G,B R, G G Different-color constraint V1 V2 V3 V2>V1 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 V2 V3 V1 Arcs to examine V1>V2 • 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