Exogenous and Endogenous Extensions of Architectural Types

The problem of formalizing architectural styles has been recently tackled with the introduction of the concept of architectural type. The internal behavior of the system components can vary from instance to instance of an architectural type in a controlled way, which preserves the absence of deadlock related architectural mismatches proved via the architectural compatibility and interoperability checks. In this paper we extend the notion of architectural type by permitting a controlled variability of the component topology as well. This is achieved by means of two kinds of topological extensions: exogenous and endogenous. An exogenous extension consists of attaching a set of new topology compliant components to a set of already existing components. An endogenous extension consists of replacing a set of already existing components with a set of new topology compliant components. We show that such a variability of the topology is still manageable from the analysis viewpoint.