Chapter 11. The ATAM: A Comprehensive Method for Architecture Evaluation

with Mark Klein

We evaluate the services that anyone renders to us according to the value he puts on them, not according to the value they have for us.

-Friedrich Nietzsche

In this chapter, we will introduce the Architecture Tradeoff Analysis Method (ATAM), a thorough and comprehensive way to evaluate a software architecture. The ATAM is so named because it reveals how well an architecture satisfies particular quality goals, and (because it recognizes that architectural decisions tend to affect more than one quality attribute) it provides insight into how quality goals interact-that is, how they trade off.

Evaluating an architecture for a large system is a complicated undertaking. First, a large system will have a comparably large architecture that will be difficult to understand in a limited amount of time. Second, according to Nietzsche and the Architecture Business Cycle (ABC), a computer system is intended to support business goals and the evaluation will need to make connections between those goals and the technical decisions. Finally, a large system usually has multiple stakeholders and acquiring their different perspectives in a limited amount of time requires careful management of an evaluation process. As you can see from this set of difficulties, managing the limited time for an architecture evaluation is a central problem.

Note: Mark Klein is a senior member of the technical staff at the Software Engineering Institute.

The ATAM is designed to elicit the business goals for the system as well as for the architecture. It is also designed to use those goals and stakeholder participation to focus the attention of the evaluators on the portion of the architecture that is central to the achievement of the goals.

This chapter will introduce the steps of the ATAM and discuss them in light of their intended purpose. It will also presents an ATAM case study (based on one of our applications of the method).