Here are differences between a Requirement and a Constraint in DO-178C or DO-178C. DO NOT mix the two together!

  • Requirements – Capture Features and Functions of a system or component.
  • Constraints – Define the Non-Functional aspects of a system or component, such as restrictions on technology, resources or techniques to be used.

Also Capture a requirement at the level where it will be tested.

  • If the “requirement” cannot be tested at the level you are working, then it should be captured at a lower or higher level.
    • Pay careful attention to the test aspects; capture any spinoff requirements for test stands or benches; so that when that time comes the test environment is ready.
  • Capture the other decisions made at each level in the “design documentation” for that level.
    • Architecture Constraints
    • Design Constraints
    • Resource Constraints
    • When capturing these constraints, do so in the design documentation.

Read this Avionics Whitepaper: Practical Rules for DO-178C Requirements Capture

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