Computer systems are used in many critical applications where a failure can have serious consequences (loss of lives or property). Developing systematic ways to relate the software quality attributes of a system to the system's architecture provides a sound basis for making objective decisions about design trade-offs and enables engineers to make reasonably accurate predictions about a system's attributes that are free from bias and hidden assumptions. The ultimate goal is the ability to quantitatively evaluate and trade off multiple software quality attributes to arrive at a better overall system. The purpose of this report is to take a small step in the direction of developing a unifying approach for reasoning about multiple software quality attributes. In this report, we define software quality, introduce a generic taxonomy of attributes, discuss the connections between the attributes, and discuss future work leading to an attribute-based methodology for evaluating software architectures.

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