Predicting the reliability and safety of commercial software in advanced avionic systems

Exploiting developments in the commercial domain for military application has been identified as a key to reducing avionic system through-life costs while improving system upgradeability. While the use of commercially available hardware components has, to some extent, been accepted as the only way forward, the use of COTS software components has been highly contentious. Although the potential benefits can still apply to software, new challenges are introduced that must be overcome. These problems are exacerbated by the inherently integrated nature of advanced avionics. The very idea of trusting COTS software in a complex real-time system that may affect, or even be responsible for, safety critical or mission critical functions has been the subject of much debate. The concerns have mainly been centred on reliability and certification. It is these areas that have provided the focus for the study described in this paper. Software failure prediction techniques have been used across many application domains, and software reliability modelling is now a highly developed area in software measurement. The results of research to determine the applicability of these techniques for avionics software are summarised with emphasis on the real-time operating system (RTOS) software. This was selected as it provides a complex component of an avionic system for which there is real scope for using COTS technology. The suitability of these techniques, and others in supporting system certification and the production of a safety case is then considered and recommendations made.