11.2 Outputs of the ATAM

An ATAM-based evaluation will produce at least the following outputs:

  • A concise presentation of the architecture. Architecture documentation is often thought to consist of the object model, a list of interfaces and their signatures, or some other voluminous list. But one of the requirements of the ATAM is that the architecture be presented in one hour, which leads to an architectural presentation that is both concise and, usually, understandable.

  • Articulation of the business goals. Frequently, the business goals presented in the ATAM are being seen by some of the development team for the first time.

  • Quality requirements in terms of a collection of scenarios. Business goals lead to quality requirements. Some of the important quality requirements are captured in the form of scenarios.

  • Mapping of architectural decisions to quality requirements. Architectural decisions can be interpreted in terms of the qualities that they support or hinder. For each quality scenario examined during an ATAM, those architectural decisions that help to achieve it are determined.

  • A set of identified sensitivity and tradeoff points. These are architectural decisions that have a marked effect on one or more quality attributes. Adopting a backup database, for example, is clearly an architectural decision as it affects reliability (positively), and so it is a sensitivity point with respect to reliability. However, keeping the backup current consumes system resources and so affects performance negatively. Hence, it is a tradeoff point between reliability and performance. Whether this decision is a risk or a nonrisk depends on whether its performance cost is excessive in the context of the quality attribute requirements of the architecture.

  • A set of risks and nonrisks. A risk is defined in the ATAM as an architectural decision that may lead to undesirable consequences in light of stated quality attribute requirements. Similarly, a nonrisk is an architectural decision that, upon analysis, is deemed safe. The identified risks can form the basis for an architectural risk mitigation plan.

  • A set of risk themes. When the analysis is complete, the evaluation team will examine the full set of discovered risks to look for over-arching themes that identify systemic weaknesses in the architecture or even in the architecture process and team. If left untreated, these risk themes will threaten the project's business goals.

The outputs are used to build a final written report that recaps the method, summarizes the proceedings, captures the scenarios and their analysis, and catalogs the findings.

There are secondary outputs as well. Very often, representations of the architecture will have been created expressly for the evaluation and may be superior to whatever existed before. This additional documentation survives the evaluation and can become part of the project's legacy. Also, the scenarios created by the participants are expressions of the business goals and requirements for the architecture and can be used to guide the architecture's evolution. Finally, the analysis contained in the final report can serve as a statement of rationale for certain architectural decisions made (or not made). The secondary outputs are tangible and enumerable.

There are intangible results of an ATAM-based evaluation. These include a palpable sense of community on the part of the stakeholders, open communication channels between the architect and the stakeholders, and a better overall understanding on the part of all participants of the architecture and its strengths and weaknesses. While these results are hard to measure, they are no less important than the others and often are the longest-lasting.

    Part Two: Creating an Architecture
    Part Four: Moving From One System to Many