We define courteous logic programs, an expressive superclass of general logic programs, for the acycic case. Courteous LP's feature not only classical negation as in extended LP's (Gelfond & Lifschitz), but also prioritized con-flict handling. We show courteous LP's always have a consistent and unique answer set, which can be computed in 0 (m2) time, where m is the size of the ground-instantiated program, as compared to 0 (m) time for general LP's. Courteous LP's provide a method to resolve conflicts that arise in authoring (specifying), updating, and merging. This is especially useful for creation of rule-based intelligent agents by non-technical authors, eg, for commercial applications such as personalized information filtering and workflow. Current work includes: implementing courteous LP's for such applications, in IBM's RAISE system; generalizing expressively, eg, to permit recursion; and developing methods for interactive acquisition of rules, eg, conflict analysis and inter-agent communication. An extended version of this paper (with proofs) is available as IBM Re-search Report RC 20836, at http://www. research. zbrn. com as are additional other related papers and pages (see author's Web address above). i Introduction and Overview

Our aim in developing courteous logic programs is to improve the expressive convenience of logic programs, especially for applications in intelligent infor-mation agents. We call the formalism" courteous" for two reasons. First, it respects precedence, ie, priority relationships between rules. Second, even in the presence of conflict between rules, it is" well-behaved" in the sense of there being a consistent, tractably computable, and unique set of conclusions.