Computing Strong and Weak Permissions in Defeasible Logic

TL;DR

This paper extends Defeasible Logic to model and compute various types of permissions, including strong and weak, with a focus on explicit norms, preferences, and computational efficiency.

Contribution

It introduces new methods for representing and reasoning about different permission concepts within Defeasible Logic, including preference and sequence operators.

Findings

Logical system has linear computational complexity.

Representation of strong permissions with and without new consequence relations.

Integration of preference and sequence operators for permissions.

Abstract

In this paper we propose an extension of Defeasible Logic to represent and compute three concepts of defeasible permission. In particular, we discuss different types of explicit permissive norms that work as exceptions to opposite obligations. Moreover, we show how strong permissions can be represented both with, and without introducing a new consequence relation for inferring conclusions from explicit permissive norms. Finally, we illustrate how a preference operator applicable to contrary-to-duty obligations can be combined with a new operator representing ordered sequences of strong permissions which derogate from prohibitions. The logical system is studied from a computational standpoint and is shown to have liner computational complexity.