Abstract: Poor software rectuirement for safety-critical systems (SCSs) is identified as a major root cause of catastrophis accidents. A system thinking based development framework for software safety requirements was built with system modeling and system analysis. For a particular analysis domain in a particular analysis level, a development method integrated with safety analysis was presented to develop software safety rectuirements. With the method, safety critical errors in software requirements arc neither likely to propagate through to other analysis domains in the same analysis level nor likely to the subsectuent analysis level. New safety rectuirements will be derived as early as errors are found in the safety analysis process. Safety evidence will be generated in the process to support the building of safety arguments.

Key words: Software safety, System thinking, Requirement engineering, Safety analysis, Integrated modular avionics system