Operational Concepts of Nonmonotonic Logics Part 2: Autoepistemic Logic

The subject of nonmonotonic reasoning is reasoning with incomplete information. One of the main approaches is autoepistemic logic in which reasoning is based on introspection. This paper aims at providing a smooth introduction to this logic, stressing its motivation and basic concepts. The meaning (semantics) of autoepistemic logic is given in terms of so-called expansions which are usually defined as solutions of a fixed-point equation. The present paper shows a more understandable, operational method for determining expansions. By improving applicability of the basic concepts to concrete examples, we hope to make a contribution to a wider usage of autoepistemic logic in practical applications.