Model Checking Contractual Protocols

This paper discusses how model checking, a technique used for the verification of behavioural requirements of dynamic systems, can be usefully deployed for the verification of contracts. A process view of agreements between parties is taken, whereby a contract is modelled as it evolves over time in terms of actions or more generally events that effect changes in its state. Modelling is done with Petri Nets in the spirit of other research work on the representation of trade procedures. The paper illustrates all the phases of the verification technique through an example and argues that the approach is useful particularly in the context of pre-contractual negotiation and contract drafting. The work reported here is part of a broader project on the development of logic-based tools for the analysis and representation of legal contracts [4].