Constructive extensibility of trustworthy component-based systems

In this paper we propose inheritance relations for a CSP-based component model (BRIC), which supports a constructive design based on composition rules that preserves desired properties such as deadlock freedom. We enhance this component model with support for extensibility via inheritance. The proposed relations allow extension of functionality, whilst preserving service conformance, which we define by means of a substitutability test. We also establish an algebraic connection between component extensibility and refinement. We illustrate our results by presenting a case study that consists of a bank system incrementally improved by inheritance.