ORDERED LOGIC - DEFEASIBLE REASONING FOR MULTIPLE AGENTS

Our goal is to provide a theoretical foundation for knowledge based ap plications which support nonmonotonic or defeasible reasoning and whic h incorporate the knowledge of multiple experts in a principled way. W e present a generalized proof theory for defeasible reasoning and brie fly explain the relationship of this system to other nonmonotonic form alisms. Then we present a proof theory and semantics for a logic that allows us to explicitly model internal perspectives or multiple agents . This ordered logic properly extends defeasible logic by allowing mor e complex precedence structure on rules. It provides a mechanism for r esolving conflicts between competing perspectives without obscuring th e opinions of those perspectives. We show which defeasible theories ca n be transformed into an equivalent theory in the new logic for multia gent reasoning and how a theory in the logic for multiagent reasoning can be transformed into an equivalent set of defeasible theories, one for each perspective or agent. We present a proof theory for quantifie d ordered logic and introduce the concept of a curtain which shields t he cognitive resources of one agent from another agent. Finally, we co nsider some examples and discuss how it is possible to specify the rel ative superiority of some experts over others in a natural way using o rdered logic.