Environment-Centric Contracts for Design of Cyber-Physical Systems

A contract splits the responsibilities between a component and its environment into a guarantee that expresses an intended property under the responsibility of the component, given that the environment fulfills the assumptions. Although current contract theories are limited to express contracts over interfaces of components, specifications that are not limited to interfaces are used in practice and are needed in order to properly express safety requirements. A framework is therefore presented, generalizing current contract theory to environment-centric contracts contracts that are not limited to the interface of components. The framework includes revised definitions of properties of contracts, as well as theorems that specifies exact conditions for when the properties hold. Furthermore, constraints are introduced, limiting the ports over which an environment-centric contract is expressed where the constraints constitute necessary conditions for the guarantee of the contract to hold in an architecture.