Dynamic Logic Programming

In this paper we investigate updates of knowledge bases repre sented by logic programs In order to represent negative information we use generalized logic programs which allow default negation not only in their bodies but also in their heads We start by introducing the notion of an update P U of a logic program P by another logic program U Subsequently we provide a precise semantic characterization of P U and study some ba sic properties of program updates In particular we show that our update programs generalize the notion of interpretation update We then extend this notion to sequences of logic programs updates P P de ning dynamic program updates thereby introduc ing the paradigm of dynamic logic programming This paradigm sig ni cantly facilitates modularization of logic programming and thus modularization of non monotonic reasoning as a whole Suppose that we are given a set of logic program modules each describing a di erent state of our knowledge of the world Di erent states may represent di erent time points or di erent sets of priorities or perhaps even di erent viewpoints Consequently program mod ules may contain mutually contradictory as well as overlapping infor mation The role of the dynamic program update is to use the mutual relationships existing between di erent states to precisely determine at any given state the declarative and the procedural semantics of the combined program resulting from all these modules Present addresses of the authors Jose Julio Alferes Dep Matematica Univ Evora and A I Centre Univ Nova de Lisboa Monte da Caparica Portugal Email jja di fct unl pt Joao A Leite A I Centre Univ Nova de Lisboa Monte da Caparica Portugal Email jleite di fct unl pt Luis Moniz Pereira A I Centre Univ Nova de Lisboa Monte da Caparica Portugal Email lmp di fct unl pt Halina Przymusinska Department of Computer Science California State Polytechnic University Pomona CA USA Email halina cs ucr edu Teodor C Przymusinski Department of Computer Science Univer sity of California Riverside CA USA Email teodor cs ucr edu