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Software Architecture Guide

ATAM Phase 1 and 2 Activities

Explanation

Section titled “Explanation”

ATAM is the Architecture Tradeoff Analysis Method (see Architecture Tradeoff Analysis Method (ATAM)). It is a structured review of an architecture. An evaluation typically takes three to four days.

Who takes part. ATAM brings together three groups: the review team, the project team and stakeholder representatives. See ATAM Roles for details.

The steps, in order.

  1. Present the method. The evaluation leader explains how the evaluation works to everyone assembled.
  2. Present the architecture. In step 3 the architect describes the architecture. The focus is on how it meets the business drivers, meaning the business goals behind the system.
  3. Identify architectural approaches. In step 4 the architect names the approaches used. They are only identified here. They are not analyzed yet.
  4. Build the utility tree. This tree starts with quality requirements at the top. It is refined down to scenarios. Each scenario has a stimulus (what happens) and a response (what the system should do). The scenarios are then prioritized. A measurement quantifies each response. See Quality Attribute Scenario.
  5. Analyze the approaches. In step 6 the team examines the approaches. Three kinds of findings appear here: architectural risks, sensitivity points and trade-off points. A sensitivity point is an architecture feature that affects the response to a quality requirement. See Sensitivity Point and Trade-off Point.
  6. Brainstorm scenarios. In step 7 the entire stakeholder group contributes a larger set of scenarios.
  7. Test the earlier analysis. In step 8 the prioritized scenarios act as test cases. They confirm the analysis done so far.
  8. Present the results. In step 9 the ATAM team presents its findings to the stakeholders. The output is an out-brief presentation, a written report, or both.

What the results contain. The risks are synthesized into risk themes. These themes show how the risks threaten the business goals of the system. See ATAM Results and ATAM Findings: Risks, Non-Risks, Sensitivity Points and Trade-off Points.

Example

Section titled “Example”

A team evaluates an online shop. The architect explains how the design supports the goal of handling holiday sales. The group builds a tree with “performance” at the top. One scenario reads: “Under a tenfold traffic spike, checkout answers within two seconds.” The team checks the design against it and notes a risk. Later, stakeholders brainstorm more scenarios and vote on them. The team uses the top ones to check its earlier findings. On the last day it presents a report.

Trade-offs

Section titled “Trade-offs”

The facts available here give no cost or benefit comparison. The method asks for several days from the review team, the project team and stakeholder representatives. See Advantages and Drawbacks of ATAM for a fuller discussion.

Checks

Section titled “Checks”
  • The evaluation plan allows about three to four days.
  • The review team, the project team and stakeholder representatives all take part.
  • The utility tree reaches the level of scenarios with stimuli, responses and priorities.
  • Risks, sensitivity points and trade-off points are recorded when approaches are analyzed.
  • Results are delivered as an out-brief and/or written report, with risks grouped into themes.
Section titled “Related”

Sources

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