Derived Requirements (Software)
Section 08: Software Certification (DO-178C)
Definition
Software requirements (at either the HLR or LLR level) that are not directly traceable to a higher-level requirement but are generated by the software development process itself. Derived requirements arise from design decisions, implementation constraints, or the need to implement functions that are necessary for the software to work correctly but that were not explicitly stated in the system requirements. Examples include requirements for initialization sequences, internal data structures, error handling mechanisms, and resource management. DO-178C requires that derived requirements be provided to the system safety assessment process because they may introduce new failure modes or modify the failure behavior assumed in the system safety analysis.
Where This Shows Up
Derived requirements are a critical interface point between the software development process and the system safety assessment process. If the software team introduces a derived requirement that creates a new potential failure path not considered in the FHA, the safety assessment must be updated. This feedback loop is essential for maintaining the integrity of the safety argument. Failure to properly identify and evaluate derived requirements is a common certification issue.
Primary Sources
Addresses derived requirements and the requirement to feed them back to the safety assessment process.
Describes the feedback of derived requirements from software development to system safety assessment.
Related Terms
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