Traceability (Bi-Directional)
Section 08: Software Certification (DO-178C)
Definition
The ability to trace relationships between lifecycle data items in both forward (from requirements to implementation and test) and backward (from implementation and test back to requirements) directions. DO-178C requires bi-directional traceability at multiple levels: (1) System requirements to HLRs and HLRs back to system requirements; (2) HLRs to LLRs and LLRs back to HLRs; (3) LLRs to source code and source code back to LLRs; (4) HLRs to test cases/procedures and test cases/procedures back to HLRs; (5) LLRs to test cases/procedures (for applicable levels) and test cases/procedures back to LLRs. Forward traceability ensures that all requirements are implemented and tested. Backward traceability ensures that all code and tests can be justified by a requirement (detecting extraneous code and unnecessary tests).
Where This Shows Up
Bi-directional traceability is one of the most labor-intensive but fundamental aspects of DO-178C compliance. It provides the objective evidence that the software implements all its requirements and only its requirements, and that all requirements are verified. Traceability gaps — requirements without corresponding code or tests, code without corresponding requirements — are common audit findings and indicate potential deficiencies in the development or verification process.
Primary Sources
Defines traceability objectives for the software verification process, including bi-directional traceability requirements at each software level.
Related Terms
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