Viewpoints on Modifiability

Software architecture is generally regarded as an important tool to achieve systems of higher quality. It is claimed that the foundation for a system’s quality is laid by the decisions made in the software architecture. A question that is occupying both researchers and practitioners is in which areas should decisions be made in the software architecture? We believe architectural view models play an important role in the answer to this question. View models consist of a coherent set of architectural views. These view models have both a prescriptive and a descriptive role in the development process. Their prescriptive role is that they call for a number of aspects to be considered when defining a software architecture and their descriptive role is that they provide a framework to document a software architecture. Currently, a number of view models exist, the most important of which are the 4+1 View Model of Kruchten and the four views by Soni et al. In our experience with modifiability analysis for business information systems we found that the views in current view models do not include all information required. In this paper we discuss the views we found useful for architecture level impact analysis of business information systems. They are illustrated using a case study we performed for the Dutch Tax Department. We claim that when these views are required for architecture level impact analysis, the decisions they capture should also be considered during architecture development.