Strong and weak contract formalism for third-party component reuse

Our aim is to contribute to bridging the gap between the justified need from industry to reuse third-party components and skepticism of the safety community in integrating and reusing components developed without real knowledge of the system context. We have developed a notion of safety contract that will help to capture safety-related information for supporting the reuse of software components in and across safety-critical systems. In this paper we present our extension of the contract formalism for specifying strong and weak assumption/guarantee contracts for out-of-context reusable components. We elaborate on notion of satisfaction, including refinement, dominance and composition check. To show the usage and the expressiveness of our extended formalism, we specify strong and weak safety contracts related to a wheel braking system.