Expressing Preferences using Preference Set Constraint Atoms
  This paper introduces an extension of Answer Set Programming called Preference Set Constraint Programming which is a convenient and general formalism to reason with preferences. PSC programming extends Set Constraint Programming introduced by Marek and Remmel (Marek and Remmel 2004) by introducing two types of preference set constraint atoms, measure preference set constraint atoms and pre-ordered preference set constraint atoms, which are extensions of set constraint atoms. We show that the question of whether a PSC program has a preferred stable model is CoNP-complete. We give examples of the uses of the preference set constraint atoms and show that Answer Set Optimization (Brewka, Niemel\"a, and Truszczynski 2003) and General Preference (Son and Pontelli 2006) can be expressed using preference set constraint atoms. 
Alex Brik, Jeffrey B. Remmel
cs.LO