A challenge in software design is to find solutions that balance and optimize the quality attributes of the application. We present a case study of an application and the results of a design decision made on weak assumptions. The application has been assessed with respect to performance and maintainability. We present and evaluate an alternative design of a critical system component. Based on interviews with the involved designers we establish the design rationale. By analyzing the evaluation data of the two alternatives and the design rationale, we conclude that the design decision was based on a general assumption that an adaptable component design should increase the maintainability of the application. This case study is clearly a counter example to that assumption, and we therefore reject it as a myth. This study shows, however, that the myth is indeed responsible for the major performance problem in the application.

In this paper we present the experiences and architecture from a research project conducted in cooperation with two industry partners.The goal of the project was to reengineer an existing system for haemo dialysis machines into a domain specific software architecture [23].Our main experiences are (1) architecture design is an iterative and incremental process, (2) software qualities require a context, (3) quality attribute assessment methods are too detailed for use during architectural design, (4) application domain concepts are not the best abstractions, (5) aesthetics guides the architect in finding potential weaknesses in the architecture, ( 6) it is extremely hard to decide when an architecture design is ready, and (7) documenting software architectures is a important problem.We also present the architecture and the design rational to give a basis for our experiences.We evaluated the resulting architecture by implementing a prototype application.

The paper presents a method for reengineering software architectures. The method explicitly addresses the quality attributes of the software architecture. Assessment of quality attributes is performed primarily using scenarios. Design transformations are done to improve quality attributes that do not satisfy the requirements. Assessment and design transformation can be performed for several iterations until all requirements are met. To illustrate the method we use the reengineering of a prototypical measurement system into a domain-specific software architecture as an example.