Ambiguity Propagating Defeasible Logic and the Well-Founded Semantics

The most recent version of defeasible logic (Nute, 1997) is related to the well-founded semantics by translating defeasible theories into normal logic programs using a simple scheme proposed in (Brewka, 2001). It is found that by introducing ambiguity propagation into this logic, the assertions of defeasible theories coincide with the well-founded models of their logic program translations. Without this addition, the two formalisms are found to disagree in important cases. A translation in the other direction is also provided. By treating default negated atoms as presumptions in defeasible logic, normal logic programs can be converted into equivalent defeasible theories.