Glossary · Requirements and interfaces
Requirement
In systems engineering, a requirement is a documented need or condition that a system or process must satisfy. A good requirement is unambiguous, verifiable and traceable to its source.
- Systems engineering
- Verification
In one sentence
What makes a requirement usable in safety engineering: documented, verifiable and traceable from stakeholder need to test and evidence.
Example
“The conveyor shall stop when the pull-cord switch is actuated” is a requirement derived from the risk assessment of a transfer point and verified by a functional test.
How it applies
- Quality: Write one requirement per statement, with “shall”, a clear subject and a verification criterion. Record its source, for example a hazard or a standard clause.
- Machine safety: Safety requirements derive from the risk assessment. Their trace back to the hazard justifies them; their trace forward to tests supports verification.
- Types: Stakeholder requirements express needs, system requirements are derived and verifiable. Functional and nonfunctional requirements describe what and how well.
- Technical documentation: Requirements for the information for use (content, warnings, languages) are requirements too and should be traced like others.
Requirement vs. constraint
A requirement states what must be satisfied. A constraint limits how it may be satisfied. Both are managed and traced the same way.