Glossary · Evidence, assurance and traceability
Assumption (systems engineering)
German: Annahme
In systems engineering, an assumption is a documented condition taken as true for a requirement, analysis, design, test, or claim. Assumptions are not proven within the work that uses them, so they must be stated, owned and monitored.
- Systems engineering
- Verification
In one sentence
An assumption is a documented condition taken as true for an analysis or claim; it must be stated, owned and checked over time.
Example
The PL calculation for a door interlock on a packaging machine assumes 10 door openings per hour; if the customer switches to manual loading with 60 openings per hour, the assumption and the result no longer hold.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Evidence: Keep an assumption register with ID, statement, owner, source and the items that depend on it. Link each assumption to the claims it supports.
- Functional safety: Demand rates, mission time, environment and user competence are typical assumptions in safety calculations. Fault exclusions are assumptions with explicit conditions.
- Technical documentation: Assumptions about users become instructions and limits in the information for use. If the manual does not state them, users cannot respect them.
- Monitoring: Field data are the natural check on assumptions. Define which data would show that an assumption is wrong.
Assumption vs. constraint
An assumption is believed to be true but not controlled by the project. A constraint is a limit imposed on the solution, such as a standard or an interface.