Nonmonotonic Reasoning - Computational Perspective

Introduction Nonmonotonic logics were introduced in the late 70s as knowledge representation formalisms. Default logic [Rei80], circumscription [McC80], autoepistemic logic [Moo85, Lev90] and logic programming with negation [ABW88, GL88, Apt90] turned out over the years to be most widely studied and most influential in the development of the area. To serve as a knowledge representation tool, a formal system must offer an expressive language with well-understood semantics, and a computational mechanism supporting effective reasoning. In this tutorial we will present theoretical foundations for default logic and logic programming. We will emphasize results that have bearing on algorithms, computational complexity and implementations. We will discuss methodology of programming with nonmonotonic knowledge representation systems and demonstrate an implementation of default logic, Default Reasoning System (or DeReS), developed in the University of Kentucky. This reader contains al