Architectural Reuse in Software Systems In-house Integration and Merge - Experiences from Industry

When organizations cooperate closely, for example after a company merger, there is typically a need to integrate their in-house developed software into one coherent system, preferably by reusing from all of the existing systems. The parts that can be reused may be arbitrarily small or large, ranging from code snippets to large self-containing components. Not only implementations can be reused however; sometimes it may be more appropriate to only reuse experiences in the form of architectural solutions and requirements. In order to investigate the circumstances under which different types of reuse are appropriate, we have performed a multiple case study, consisting of nine cases. Our conclusions are, summarized: reuse of components from one system requires reuse of architectural solutions from the same system; merge of architectural solutions cannot occur unless the solutions already are similar, or if some solutions from one are incorporated into the other. In addition, by hierarchically decomposing the systems we make the same observations. Finally, among the cases we find more architectural similarities than might had been expected, due to common domain standards and common solutions within a domain. Although these observations, when presented, should not be surprising, our experiences from the cases show that in practice organizations have failed to recognize when the necessary prerequisites for reuse have not been present.