Contracts-refinement proof system for component-based embedded systems

Abstract

Contract-based design is an emerging paradigm for the design of complex systems, where each component is associated with a contract, i.e., a clear description of the expected interaction of the component with its environment. Contracts specify the expected behavior of a component by defining the assumptions that must be satisfied by the environment and the guarantees satisfied by the component in response. The ultimate goal of contract-based design is to allow for compositional reasoning, stepwise refinement, and a principled reuse of components that are already pre-designed, or designed independently.In this paper, we present fully formal contract framework based on temporal logic (a preliminary version of this framework has been presented in [1]). The synchronous or asynchronous decomposition of a component into subcomponents is complemented with the corresponding refinement of its contracts. The framework exploits such decomposition to automatically generate a set of proof obligations. Once verified, the conditions allow concluding the correctness of the architecture. This means that the components ensure the guarantee of the system and the system ensures the assumptions of the components. The framework can be instantiated with different temporal logics. The proof system reduces the correctness of contracts refinement to entailment of temporal logic formulas. The tool support relies on an expressive property specification language, conceived for the formalization of embedded system requirements, and on a verification engine based on automated SMT techniques.