# Quality Attribute

**In short:** A quality attribute describes how well a system meets stakeholder needs, such as speed or security. Teams write them as specific, measurable scenarios because they strongly shape architectural decisions.

## Explanation

A quality attribute is a property of a system that shows how well it meets what stakeholders need. Stakeholders are the people with an interest in the system. ISO/IEC 25010 defines system quality as the degree to which a system satisfies stated and implied needs. See the article "ISO/IEC 25010 Product Quality Model" for details.

**A catalog of qualities.** The ISO/IEC 25010 product quality model lists nine quality characteristics. Examples are functional suitability, performance efficiency, compatibility and interaction capability.

**Why the word "quality" alone is not enough.** The term is vague and broad. A requirement like "the system must be of high quality" cannot be built or tested. Quality requirements must describe stakeholder expectations in a specific and measurable way.

**Scenarios make qualities concrete.** A quality scenario is a short description of a situation and the expected outcome. Scenarios turn vague quality requirements into concrete ones. They should be specific and measurable. They are a practical way to document what quality is required. Bass et al. at the SEI coined the term "quality attribute scenarios" for this kind of structured requirement. See "Quality Attribute Scenario".

**Two kinds of scenarios.** arc42 separates two kinds:

- Usage scenarios describe how the running system reacts to a stimulus.
- Change scenarios describe a modification or extension of the system.

This maps to qualities that show up at runtime and qualities that show up when people change the system.

**Influence on architecture.** Quality requirements strongly influence architectural decisions. For this reason, arc42 gives them their own section. See "arc42 Quality Requirements".

## Example

A team writes "the shop must be fast." Nobody can test that. They rewrite it as a usage scenario: a customer submits an order, and the system confirms it within a stated time limit. They also write a change scenario: a developer adds a new payment method, and the work stays within a stated effort. Both statements are specific and measurable, so the team can check them and use them when choosing a design.

## Trade-offs

The supplied facts do not describe trade-offs between qualities. Writing scenarios takes effort, but it replaces vague wishes with statements that people can check.



## Checks

- Quality requirements are written as specific, measurable scenarios, not as vague terms like "high quality".
- The document separates usage scenarios (runtime reaction to a stimulus) from change scenarios (modifying the system).
- Quality requirements have their own section, and architectural decisions refer to them.

## Related

- [Quality Attribute Scenario](https://arc.fuet.ch/concepts/quality-attributes/quality-attribute-scenario.md)
- [arc42 Quality Requirements](https://arc.fuet.ch/concepts/documentation/arc42-quality-requirements.md)
- [ISO/IEC 25010 Product Quality Model](https://arc.fuet.ch/concepts/quality-attributes/iso-iec-25010-quality-model.md)
- [Architecturally Significant Requirement](https://arc.fuet.ch/concepts/forces-decisions/architecturally-significant-requirement.md)
- [Quality Attribute Trade-off](https://arc.fuet.ch/concepts/quality-attributes/architectural-trade-off-thinking.md)
- [SMART Requirements](https://arc.fuet.ch/concepts/functional-requirements/smart-requirements.md)
- [Architectural Tactic](https://arc.fuet.ch/concepts/tactics/architectural-tactic.md)
- [Standard Quality Attribute List](https://arc.fuet.ch/concepts/quality-attributes/standard-quality-attribute-checklist.md)

## Sources

- [ISO 25010](https://iso25000.com/index.php/en/iso-25000-standards/iso-25010) — iso25000.com, accessed 2026-11-08
- [10 - Quality | arc42 Documentation](https://docs.arc42.org/section-10/) — docs.arc42.org, accessed 2026-11-08
- [How to specify quality requirements | arc42 Quality Model](https://quality.arc42.org/articles/specify-quality-requirements) — quality.arc42.org, accessed 2026-11-08