Requirements Phase

 

The Requirements Phase uses the outputs of the System Lifecycle Process to develop the High Level Requirements. These High Level Requirements include functional, performance, interface, and safety-related requirements, ref. DO-178B Section 5.1.

 

The inputs to the Requirements Phase are as follows:

 

• System Requirements Data (SRD) allocated to software
• Hardware Interfaces and System Architecture
• Software Development Plan
• Software Requirements, Design, and Coding Standards (SRDCS)

 

The outputs to the Requirements Phase are as follows:

 

• Software High Level Requirements Document (SHLRD)
• Software High Level Signal Dictionary (SHLSD)

 

Software High Level Requirements Document (SHLRD)

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The Software High Level Requirements Document partitions and lists the high level requirements of the software item using functional decomposition to differentiate the functionality of the subcomponents. This includes operational, behavioral, and functional requirements. Derived high level requirements should be provided to the system safety assessment process. The V&V phase activities should commence as soon as a baseline of the SHLRD can be established in CM, including reviews for clarity, consistency, and most important testability.

 

Software High Level Signal Dictionary (SHLSD)

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The High level signal dictionary is used to capture a consolidated and universal list of all Input and Output signals to the software from a board level perspective in order to generate requirements that are testable from "end to end". Ideally, this signal dictionary would be directly traceable to system level signals and schematics with a standardized naming convention for all signals.