Quality Attribute Scenario Block
Document quality attribute scenarios using the SEI format with stimulus, source, environment, artifact, response, and response measure. Define measurable architecture requirements.
The Quality Attribute Scenario block documents non-functional requirements using the Software Engineering Institute (SEI) scenario format. Each scenario specifies a stimulus, its source, the environment, the affected artifact, the expected response, and a measurable response measure.
When to Use
Block Properties
| Property | Required | Description |
|---|---|---|
| Quality Attribute | Yes | The quality being specified (e.g., Performance, Availability) |
| Source of Stimulus | No | What or who generates the stimulus |
| Stimulus | Yes | The event or condition that occurs |
| Environment | No | The conditions under which this occurs |
| Artifact | No | The system element being stimulated |
| Response | No | How the system should respond |
| Response Measure | No | How the response is measured (quantifiable) |
Quality Attribute Types
SEI Scenario Format
| Element | Description |
|---|---|
| Source | An entity (human, computer system, etc.) that generates the stimulus |
| Stimulus | A condition that requires a response when it arrives at the system |
| Environment | The stimulus occurs under certain conditions |
| Artifact | Some artifact is stimulated (the whole system or parts) |
| Response | The response to the stimulus that should be measurable |
| Response Measure | When the response occurs, it should be measurable |
Example: Performance Scenario
A latency requirement for API response times.
Example: Availability Scenario
A high availability requirement for critical services.
Example: Security Scenario
A security requirement for authentication protection.
Example: Scalability Scenario
A horizontal scaling requirement.
Example: Modifiability Scenario
A maintainability requirement for code changes.
Best Practices
| Practice | Description |
|---|---|
| Quantifiable Measures | Make response measures specific and quantifiable |
| Realistic Conditions | Define realistic stimulus conditions based on expected usage |
| Clear Environment | Specify the environment clearly (normal vs peak vs failure modes) |
| Single Attribute | Focus on one quality attribute per scenario |
| Stakeholder Review | Review scenarios with stakeholders for business alignment |
| Testing Input | Use scenarios as input for architecture decisions and testing |