The project can use NASA-STD-8739.8 to perform its determination of the software safety criticality. The software safety litmus test in Appendix A.1 of the Standard is applicable to all projects. The software is considered safety critical if it meets any of the three major criteria listed in the appendix. If the project is determined to be safety critical, then the project must adhere to the applicable statements in NASA-STD-8719.13.
As noted in NASA-STD-8719.13, non safety-critical software residing with safety-critical software is a concern because it may fail in a way that it disables or impairs the functioning of the safety-critical software. When methods to separate the code, such as partitioning, can't be used to limit the software defined as safety critical, care must be exercised to assure safety for a block of software (multiple CSCI) where only a portion are safety critical, and or for individual safety critical CSC's within a larger CSCI.
NASA-STD-8719.13 requires the software safety criticality to be re-assessed periodically (typically at each major milestone review) by the project's responsible software assurance engineer. This individual evaluates the project software for determination of safety criticality utilizing the Software Safety Litmus Test within NASA-STD-8719.13. This allows the software safety requirements to be refined and applied to the required areas (preventing a possibly costly over-application or a non-compliant and risky under application). It also assures that requirements are met and/or changes to the software are addressed and checked for safety criticality.
The software safety criticality assessment process and the location of the assessment results are documented within the Software Safety Plan (or equivalent). Most projects document the software safety criticality with the software classification. The project's system safety documentation also addresses it.
A best practice is to document the software safety criticality assessment results with the software classification assessment, with local S&MA and the Engineering TA both approving the results. An example form is provided in NASA-STD-8719.13.