Although the quality of a system's software architecture is one of the critical factors in its overall quality, the architecture is simply a means to an end, the end being the implemented system. Thus the ultimate measure of the quality of the software architecture lies in the implemented system, in how well it satis?es the system and project requirements and constraints and whether it can be maintained and evolved successfully. In order to treat design as a science rather thananart,weneedtobeabletoaddressthequalityofthesoftwarearchitecture directly, not simply as it is re?ected in the implemented system. Therefore, QoSA is concerned with software architecture quality directly by addressing the problems of: - Designing software architectures of good quality - De?ning, measuring, evaluating architecture quality - Managing architecture quality, tying it upstream to requirements and do- stream to implementation, and preserving architecture quality throughout the lifetime of the system Cross-cutting these problems is the question of the nature of software archit- ture. Software architecture organizes a system, partitioning it into elements and de?ning relationships among the elements. For this we often use multiple views, each with a di?erent organizing principle.
