Low-Level Requirements
LLRSection 08: Software Certification (DO-178C)
Definition
Software requirements that are developed from the high-level requirements to provide a more detailed description of the software behavior, closer to the implementation level. Low-level requirements are derived from the software architecture and detailed design process. They describe the software behavior at a level of detail sufficient to enable coding without further design interpretation. LLRs include algorithm details, data structure definitions, input/output descriptions, error handling logic, and timing requirements. Each LLR must be traceable to the HLR(s) from which it was derived, and the source code must be traceable to LLRs.
Where This Shows Up
LLRs bridge the gap between the abstract HLRs and the concrete source code. In DO-178C, LLRs are sometimes referred to as software design requirements. The distinction between HLR and LLR is one of abstraction level: HLRs are what the software must do (derived from system requirements), while LLRs are how the software architecture implements those functions (derived from the design process). For Levels A and B, LLRs must be verified with independence.
Primary Sources
Defines the software design process including low-level requirements development and review objectives.
Artifacts Produced
Document containing the software architecture and low-level requirements, describing the design of the software item.
Related Terms
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