Reason Based Logic and legal knowledge representation

H.B. Verheij

Abstract

Since legal rules are defeasible in nature and can be in conflict, special features are required to model legal reasoning. The idea proposed in this paper to deal with these aspects is to consider a rule as a reason-generator. The condition of a rule is merely regarded as a possible reason for its conclusion. Other reasons considering that conclusion originating from other rules, can influence the actual derivation. In case of a conflict, explicit knowledge for resolution is needed: the relative weights of all the relevant reasons is needed to derive a conclusion.

This idea is supplemented by the notion of rule applicability. The applicability of a rule means that its condition actually becomes a reason for its conclusion. By using this notion the condition of a rule is a reason for the rule's conclusion if and only if it is satisfied. There can be reasons that make the rule applicable, even though its condition is not satisfied, or inapplicable, even though its condition is satisfied.

This results in a formal framework called Reason Based Logic. Several examples show how the ideas can be applied in the field of law.

Reference:
Verheij, H. B. (1994). Reason Based Logic and legal knowledge representation. Proceedings of the Fourth National Conference on Law, Computers and Artificial Intelligence (eds. I. Carr and A. Narayanan), pp. 154-165. University of Exeter. Also published as report SKBS/B3.A/94-05.

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