Lexicographically-ordered constraint satisfaction problems

Abstract. We describe a simple CSP formalism for handling multi-attribute preference problems with hard constraints, one that combines hard constraints and preferences so the two are easily distinguished conceptually and for purposes of problem solving. Preferences are represented as a lexicographic order over complete assignments based on variable importance and rankings of values in each domain. Feasibility constraints are treated in the usual manner. Since the preference representation is ordinal in character, these problems can be solved with algorithms that do not require evaluations to be represented explicitly. This includes ordinary CSP algorithms, although these cannot stop searching until all solutions have been checked, with the important exception of heuristics that follow the preference order (lexical variable and value ordering). We describe relations between lexicographic CSPs and more general soft constraint formalisms and show how a full lexicographic ordering can be e...

• Type: Journal
• Year: 2010
• Where: CONSTRAINTS
• Authors: Eugene C. Freuder, Robert Heffernan, Richard J. Wallace, Nic Wilson
• Keywords: CONSTRAINTS 2010, Hard Constraints, Lexicographic, Lexicographic Csps