Legal Modelling and Reasoning Using Institutions

To safeguard fairness for all parties involved and proper procedure, actions within a legal context are heavily constrained. Detailed laws determine when actions are permissible and admissible. However, these restrictions do not prevent participants from acting. In this paper we present a methodology to sup­ port legal reasoning using institutions—systems that specify the normative be­ haviour of participants—and a corresponding computational model. We show how it provides a useful separation between the identification of real world ac­ tions, if and how they affect the legal model and how consequences within the legal model can be specified and verified. Thus, it is possible to define a context, introduce a real-world event and examine how this changes the state of the le­ gal model: hence, the modeller can explore both model adequacy and that of the legal framework from which it is derived, as well as offering a machine-usable legal ‘oracle’ for software components. We illustrate the use of our framework by modelling contract cancellation under Japanese contract law.