Toshiko Wakaki, Ken Satoh and Katsumi Nitta

Abstract:
To treat dynamic preferences correctly is inevitably required in legal reasoning. In this paper, we present a method which enables us to handle some class of dynamic preferences in the framework of circumscription and to consistently compute its metalevel and object-level reasoning by expressing them in an extended logic program. This is achieved on the basis of policy axioms and priority axioms which permit as to describe circumscription policy by axioms and play a role in intervening between metalevel and object-level reasoning. Not only the preference information among rules and metarules but also relations between dynamic preferences and priority axioms in circumscription are represented by a normal logic program. Thus, priorities can be derived from the preferences dynamically, which allows us to compute objectlevel circumscriptive theory using logic programming based on Wakaki and Satoh's method.

Keywords: Dynamic preferences, Policy axioms, Prioritized circumscription, Extended logic programs, Answer set semantics