Normal default logic, the fragment of default logic obtained by restricting defaults to rules of the form α:Mβ β, is the most important and widely studied part of default logic. In [MNR94], we proved a basis theorem for extensions of recursive propositional logic normal default theories and hence

this paper we formalize default reasoning processes (based on normal default theories) by temporal models. This enables us to integrate process aspects of the reasoning in the semantics in an explicit manner. The branching character of these reasoning processes is described by branching time

is to prove that PFM translation functions exist (or do not exist) between certain logics. As a result, non-monotonic logics can be arranged to form a hierarchy. This paper gives an overview of the current expressive power hierarchy (EPH) and investigates semi-normal default logic as well as prerequisite

This paper presents a methodology for testing general non-monotonic knowledge bases for logical and semantic inconsistencies. It extends the CTMS-based verification framework introduced in our previous work with an additional integrity test. This test aims to ensure that a logically consistent non-monotonic knowledge base is also free of semantic inconsistencies, resulted from violated integrity constraints. Generally, semantic inconsistencies are detected during dynamic validation of the KBS. We argue, however, that some types of semantic inconsistencies can be explicated during the formal V&V analysis, and we describe a logical procedure that carries out this validation task.

This paper presents a methodology for testing general non-monotonic knowledge bases for logical and semantic inconsistencies. It extends the CTMS-based verification framework introduced in our previous work with an additional integrity test. This test aims to ensure that a logically consistent non-monotonic knowledge base is also free of semantic inconsistencies, resulted from violated integrity constraints. Generally, semantic inconsistencies are detected during dynamic validation of the KBS. We argue, however, that some types of semantic inconsistencies can be explicated during the formal V&V analysis, and we describe a logical procedure that carries out this validation task.

The lexicographic closure of any given finite set D of normal defaults is defined. A conditional assertion a b is in this lexicographic closure if, given the defaults D and the fact a, one would conclude b. The lexicographic closure is essentially a rational extension of D, and of its rational

A serious defect with the Halpern-Pearl (HP) definition of causality is repaired by combining a theory of causality with a theory of defaults. In addition, it is shown that (despite a claim to the contrary) a cause according to the HP condition need not be a single conjunct. A definition

Cognitively demanding tasks that evoke activation in the brain's central-executive network (CEN) have been consistently shown to evoke decreased activation (deactivation) in the default-mode network (DMN). The neural mechanisms underlying this switch between activation and deactivation

(corresponding to circumscription). We show that, surprisingly enough, the important class of defaults, normal defaults with prerequisites, do not have such a modular translation into circumscription (abnormality theory). We also establish the classes of defaults which are translatable into circumscription

as the basis for specificity-based priorities for normal default theories: for each rule there is a context where it may not be defeated by any other rule. A method for computing priorities according to the principle is given. Connection to earlier work is discussed.