Glossary · Requirements and interfaces
Software requirement
German: Softwareanforderung
In systems engineering, a software requirement is a requirement allocated to software, stating a function, behavior, performance, interface or constraint the software must meet.
- Systems engineering
In one sentence
A software requirement states a function, behavior, performance, interface or constraint that the software must meet.
Example
The PLC software shall stop the conveyor within 100 ms after the jam sensor signals a blockage for longer than 2 s.
How it applies
- Engineering: Software requirements are derived from system or subsystem requirements and collected in the Software requirements specification (SRS).
- Functional safety: Safety-related software requirements must be identifiable, verifiable and traceable to the safety function they implement.
- Documentation: Alarm texts, operator messages and mode behavior often originate in software requirements; the documentation team should review them for wording that will appear on the HMI.
- Quality: Good software requirements are unambiguous, testable and free of design decisions; each should have a Requirement identifier and a Verification method.
Software requirement vs. hardware requirement
See Hardware requirement. A function allocated partly to software and partly to hardware needs both, plus an Interface requirement between them.
Software requirements should also state what the software must not do, for example start motion without an explicit command.