Legal contractions

Abstract

This paper systematically investigates how to model legal contraction in an expressive variant of Defeasible Deontic Logic. We argue that legal contraction is an umbrella concept that includes operations which are conceptually and technically different: removing rules, adding exceptions, and modifying rule priorities. The peculiarities of deleting legal conclusions show that an extension of those operations is sometimes needed, which works on the indirect conclusions from which the target effect of the contraction is obtained. The proposed techniques are discussed in the context of a new version for the logic of AGM postulates of contraction.

An ASP Implementation of Defeasible Deontic Logic

“…No. of cases (use cases-size) DDL ASP 100 (10-10) 0.039 0.041 600 (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) 0.186 0.180 1500 0.515 0.439…”

“…[5] provides the ambiguity propagation companion of the encoding we presented here for constitutive rules, and it can be incorporated almost directly in the current encoding 8 . Furthermore, we argued [27] that the two variants are needed to handle deontic ambiguities, and we provided examples where the two forms of reasoning need to be integrated in a deontic setting. To the best of our knowledge, the Defeasible Deontic Logic of [27], a conservative extension of the logic presented in this paper, is the only formalism that currently supports the integration of the two variants.…”

“…Furthermore, we argued [27] that the two variants are needed to handle deontic ambiguities, and we provided examples where the two forms of reasoning need to be integrated in a deontic setting. To the best of our knowledge, the Defeasible Deontic Logic of [27], a conservative extension of the logic presented in this paper, is the only formalism that currently supports the integration of the two variants. The encoding we presented can be easily extended to incorporate the logic proposed in [27].…”

“…To the best of our knowledge, the Defeasible Deontic Logic of [27], a conservative extension of the logic presented in this paper, is the only formalism that currently supports the integration of the two variants. The encoding we presented can be easily extended to incorporate the logic proposed in [27].…”