Towards formalizing behavioral substitutability in component frameworks

When using a component framework, developers need to respect the behavior implemented by the components. Static information about the component interface is not sufficient. Dynamic information such as the description of valid sequences of operations is required. In this paper we propose a mathematical model and a formal language to describe the knowledge about behavior We rely on a hierarchical model of deterministic finite state-machines. The execution model of these state-machines follows the Synchronous Paradigm. We focus on extension of components, owing to the notion of behavioral substitutability. A formal semantics for the language is defined and a compositionality result allows us to get modular model-checking facilities. From the language and the model, we can draw practical design rules that are sufficient to preserve behavorial substitutability. Associated tools may ensure correct (re)use of components, as well as automatic simulation and verification, code generation, and run-time checks.