  Stable Model Semantics and Well Founded Semantics have been shown to be very
useful in several applications of non-monotonic reasoning. However, Stable
Models presents a high computational complexity, whereas Well Founded Semantics
is easy to compute and provides an approximation of Stable Models. Efficient
engines exist for both semantics of logic programs. This work presents a
computational integration of two of such systems, namely XSB and SMODELS. The
resulting system is called XNMR, and provides an interactive system for the
exploration of both semantics. Aspects such as modularity can be exploited in
order to ease debugging of large knowledge bases with the usual Prolog
debugging techniques and an interactive environment. Besides, the use of a full
Prolog system as a front-end to a Stable Models engine augments the language
usually accepted by such systems.
