3 Requirements, Constraints, and Verification
3.1 Make needs testable
A statement such as the device should be reliable is a useful wish but not yet a testable design requirement. Prefer a statement such as the device shall complete at least 995 out of 1,000 specified operating cycles under the defined test conditions.
A robust requirement identifies a subject, a measurable threshold, and the environment or conditions under which it must hold.
3.2 Separate types of requirements
- Functional: What must it do?
- Performance: How well or how quickly must it do it?
- Interface: How must it connect to people, systems, or other components?
- Safety/regulatory: Which limits are mandatory?
- Resource: Which budget, mass, power, or schedule restrictions apply?
3.3 A traceability table
| ID | Requirement | Verification method | Evidence |
|---|---|---|---|
| R-01 | System operates for 8 hours on specified battery | Endurance test | To be collected |
| R-02 | Enclosure meets specified ingress requirements | Applicable test procedure | To be collected |
| R-03 | User can stop motion within 1 second | Timed test | To be collected |
These are illustrative requirements, not universal safety standards.
Exercise: Rewrite three vague objectives as measurable shall-statements and define one test for each.
Note
Living chapter. This is an initial working treatment. Derivations, examples, and references will be expanded in future editions.