Component Service Promotion: Contracts, Mechanisms and Safety

Composition is a core concept of component and service-based models. In hierarchical component composition, promotion is used to make services available at a higher level of the hierarchy without breaking encapsulation. In this article we will study different kinds of promotion of services equipped with contracts, their usefulness, as well as their safety by considering appropriate proof obligations. We introduce several explicit assertion constructs in order to reduce the proof effort. We study the impact of encapsulation and rich state description on these promotions. We illustrate the approach (specification and verification) with the Kmelia component language.