Where Fail-Safe Default Logics Fail

TL;DR

This paper examines the failure condition in Reiter's default logic, revealing it as a necessary computational feature for domain encoding rather than a semantic flaw.

Contribution

It reinterprets the failure condition in default logic as a computational aspect essential for encoding certain domains, challenging previous semantic-focused views.

Findings

Failure is a computational feature, not a semantic problem.

Failure enables encoding of complex domains into default logic.

Revises understanding of default logic's limitations and capabilities.

Abstract

Reiter's original definition of default logic allows for the application of a default that contradicts a previously applied one. We call failure this condition. The possibility of generating failures has been in the past considered as a semantical problem, and variants have been proposed to solve it. We show that it is instead a computational feature that is needed to encode some domains into default logic.