Validating software architectures for high reliability

In this paper, we present a generic approach for quantitatively evaluating the performance implications of a software architecture using the concept of operational profile from software reliability engineering. In our approach, the System Under Development (SUD) modes of operation are analyzed to specify a mode's rate of arrivals of external events. The requests' process flow (i.e., the rate of arrival of internal requests at server processes) is then derived from the software architecture. Finally, the product of the internal arrival rates and the amount of server resources to service a request is used to calculate a mode's server resource utilization. Application of this technique to an actual AT&T telecommunications operations system, together with implications for engineering software architectures that are robust under variation in modes of operation are discussed.