A Calculus Supporting Contract Reasoning and Monitoring

Over these past years, formal reasoning about contracts between parties participating in a transaction has been increasingly explored in the literature. There has been a shift of view from one viewing contracts simply as properties to be satisfied by the parties, to one in which contracts are considered as first class syntactic objects and which can be reasoned about independently of the parties' behavior. In this paper, we present a contract calculus to reason about contracts abstracting the parties' behavior using a simulation relation-effectively a calculus of contracts regulating interaction between parties. We show how the calculus can be used to support the runtime monitoring of contracts and apply it to a plane boarding system case study.