Formalizing Non-Monotonic Reasoning Systems

In recent years, there has been considerable interest in non-monotonic reasoning systems. Unfortunately, formal rigor has not always kept pace with the enthusiastic propagation of new systems. Formalizing such systems may yield dividends in terms of both clarity and correctness. We show that Default Logic is a useful tool for the specification and description of non-monotonic systems, and present new results which enhance this usefulness.