The aim of the proposed research is to answer several questions regarding adequately formalizing common sense reasoning. There will be three steps. First, to evaluate and classify some of the knowledge representation languages, in particular, to compare various semantics of logic programs and develop benchmark programs that distinguish them. Second, to consider features that are not handled by the traditional nonmonotonic formalisms and suggest methods to handle them. The particular features considered are: defining the consistency of a set of default and strict rules, and being able to infer new defaults from a set of default and strict rules. Third, to develop a prototype system to answer queries with respect to more general knowledge representation language than can be handled by the systems developed so far, in particular, to follow the lead of systems based on the well founded semantics of normal logic programs to develop a prototype system to answer queries with respect to the well founded semantics of a default theory. The significance of the proposed research is that if successful it makes both theoretical advances in formalizing common sense reasoning and provides a prototype implementation of query answering system for a more general formalism. //
