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 support legal reasoning using institutions—systems that specify the normative behaviour of participants—and a corresponding computational model. We show how it provides a useful separation between the identification of real world actions, 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 legal 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.