Requirements, configuration management and traceability for safety critical software

Software requirements are the focal point from which traceability to all related artifacts are established during the certification of safety critical software. For the certification of air-borne software, the guidance document DO-178B, requires that the link between requirements, design, code and tests be documented and verified. The DO-178B document does not describe how this should be done, but it permits the reengineering of information that is missing, to support the certification of commercial-off-the-shelf (COTS) products. Requirements were entered in a database and evolved through a sequence that enforced the states described in company process documents. The design descriptions, source code, tests, results and so on were maintained in a configuration management (CM) system. The final audit was successful and the CD-ROM delivery of a requirements based certification package was accepted and commended. The details of the approach and the lessons learned were presented.