Experiences from the Architectural Change Process

A good software architecture is becoming recognized as a major factor for successful products. There has been much research on the technical aspects of software architecture and it is recognized that the driving requirements for architectures are "non-functional", but few have studied how organizations decide on architectural changes. In this paper we study the topic through several case studies. The changes to the architecture are in all cases changes to the "non-functional" requirements on the system. Issues that we want to evaluate are: when and how is the need for an architectural change discovered; what is the underlying non-functional requirement; who drives the change; how is it prepared and evaluated; and finally, who makes the decision and how is it implemented. Through interviews with people that have experience from architectural changes we compare the decision process for architectural changes to the ordinary functional requirement change process and the organizational change process. We find that architectural changes have aspects of both functional and organizational changes. An architectural change does not only need to be technically sound, it also needs to be anchored firmly in the organization. This report gives both architects and managers guidelines to balance short-term project goals and longterm organizational goals with respect to architecture.