Evaluation of Software Architectures for a Control System: a Case Study

In this paper, we give our view on the software architecture phase in the development process. During this phase, we distinguish mo-deling and structuring activities. A system is modeled according to a certain approach, and this model is used to instantiate a certain architectural style. In general, the activities are intertwined. The choice for a certain software architecture has implications on the non-functional properties of the system. We illustrate our view with a case study of a software controller for a (toy) railroad system which we have available in our software lab. Several models of this system, expressed in formal speciication languages, were made in the past, so we are able to produce a software architecture for the system while carrying out both activities separately. The resulting software architectures are evaluated with respect to timing aspects, scalability, fault-tolerance, and extendibility. Extendibility of a software system is especially important for domains were changes should be applicable on-line. Design for change should start at the software architectural level.