A Non-monotonic Logic for Specifying and Querying Preferences

Preferences are becoming of greater interest in many areas of artificial intelligence, such as knowledge representation, multiagent systems, constraint satisfaction, decision making, and decision-theoretic planning. In the logic of preference there is a debate when a set of preferences should be consistent. For example, Bacchus and Grove [1996] criticize ceteris paribus preferences, because {p > ¬p,¬p ∧ q > p ∧ q} should be consistent, and they criticize most existing logics of preference, because {p > ¬p, q > ¬q,¬(p∧ q) > p∧ q} should be consistent. In order not to restrict the use of the logic of preference, we propose a minimal logic of preference in which any set of specified preferences is consistent. To make it useful for practical applications, we extend this logic to specify preferences with a logic to query preferences, and with a nonmonotonic reasoning mechanism.