Middleware Models for Dynamic Software Architectures

Component technology is a new promising approach to the development of complex, reusable distributed systems in that it separates the application concerns into components that can be programmed separately and assembled together through processes of composition. Architecture description languages provide suitable notations to describe the systems architecture in terms of components, with well-de ned interfaces, connectors and the architectural con guration, where components and instances are created and glued. The middleware provides the infra-structure in which components can be executed and interact in a transparent manner. A limitation of existing (algebraic) formal component models is that they are static, which means that the architectural con guration cannot be recon gured during execution. This problem can be the result of existing algebraic formalisms (process algebras) applied to communicating systems, which usually only support static networks of processes. This paper examines the formal modelling of dynamic recon guration and presents results that demonstrate that realistic recon guration models can be formulated using static formal models. This is illustrated with examples of two recon guration models speci ed in CSPM , a dialect of CSP used by the FDR2 model checker.