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Software Architecture Guide

Advantages and Drawbacks of ATAM

Explanation

Section titled “Explanation”

ATAM is the Architecture Tradeoff Analysis Method, a structured way to evaluate a software architecture. The article Architecture Tradeoff Analysis Method (ATAM) covers the method itself. This article covers what it gives you and what it costs.

Advantages

  • Risks show up early. The evaluation finds risks while the project is still young.
  • Quality requirements become clearer. Quality requirements say how well a system must work, such as how fast or how available it must be. ATAM pushes teams to state them clearly.
  • Documentation improves. The architecture description gets better. The reasons behind architectural decisions get written down.
  • Stakeholders talk more. Stakeholders are people with an interest in the system. The evaluation increases communication among them.

What you get out

An ATAM produces an out-brief presentation, a written report, or both. The report lists risks and non-risks. It also contains a utility tree of the requirements that drive the architecture. See ATAM Results and ATAM Findings: Risks, Non-Risks, Sensitivity Points and Trade-off Points.

Cost

A full ATAM typically takes three to four days. It gathers an evaluation team, the architects and stakeholder representatives. One source puts a medium-size evaluation at about 70 person-days across all participants, and small projects at about 32. Another source gives a wider range: two days to several weeks. The number of stakeholders and scenarios drives that range.

Ways to reduce the cost

  • Reuse recorded scenarios from earlier evaluations. Over time they work like a checklist.
  • On smaller projects, this can halve the effort.
  • Use a lighter method. Lightweight alternatives such as DCAR, pre-mortem and PBAR trade thoroughness for speed. See Lightweight ATAM.

Example

Section titled “Example”

A team plans an evaluation for a mid-size system. They expect to need several days and many people. Before the workshop, they reuse scenarios recorded in an earlier evaluation. The workshop forces them to write precise quality requirements. The final report lists risks and non-risks. The team then updates its decision records.

Trade-offs

Section titled “Trade-offs”

A full ATAM costs a lot of time and many people. Reuse of scenarios and smaller scope lower that cost. Lightweight alternatives are faster but less thorough. PBAR, for example, finds only some risks quickly. DCAR can take as long as ATAM if it evaluates all significant decisions. Choose the depth that fits the project size and the risk you face.

Checks

Section titled “Checks”
  • The architecture evaluation produced a written report or out-brief that lists risks and non-risks.
  • The effort for the evaluation (duration, participants) was estimated before it started.
  • The team considered reusing recorded scenarios or a lighter method to reduce evaluation cost.
Section titled “Related”

Sources

Section titled “Sources”