On Warranted Inference in Possibilistic Defeasible Logic Programming

Possibilistic Defeasible Logic Programming (P-DeLP) is a logic programming language which combines features from argumentation theory and logic programming, incorporating as well the treatment of possibilistic uncertainty and fuzzy knowledge at object-language level. Defeasible argumentation in general and P-DeLP in particular provide a way of modelling non-monotonic inference. From a logical viewpoint, capturing defeasible inference relationships for modelling argument and warrant is particularly important, as well as the study of their logical properties. This paper analyzes a non-monotonic operator for P-DeLP which models the expansion of a given program P by adding new weighed facts associated with warranted literals. Different logical properties are studied and contrasted with a traditional SLD-based Horn logic, providing useful comparison criteria that can be extended and applied to other argumentation frameworks.