Model based safety analysis: Automatic generation of safety validation test cases

Safety Assurance and validation of embedded airborne systems are challenging today, despite various advances in the field of software engineering. Model based software engineering, can bring in visibility to safety assurance process by basing analysis on a single comprehensive model. AADL is one such architecture modelling language suitable for modelling avionics systems. It can be used for systematic modelling of safety critical systems[2]. Safety requirements can be broadly categorised into domain specific and execution platform specific. Both categories of safety requirements can be modelled in AADL. The model then can be analysed to generate fault trees representing functional hazards. Test cases for validation of mitigation of hazards can be generated automatically from the model. But mere avoidance of the hazards, is not enough for safety validation as there are various assumptions, decisions and timing aspects to be validated to be true in the nominal and fault scenarios in the operating environment. This paper focuses on automatic generation of comprehensive test cases based on the above aspects, which can be used for safety validation, at system level. The tool developed for the purpose is presented with an example from avionics domain and results are discussed.