Template-based formalization of safety functions and analyses

We present a template for gathering and structuring all information required by a human or software to perform a failure-mode-and-effects analysis (FMEA). Instead of introducing new theoretical concepts, we help practitioners in improving and accelerate their work. Indeed, FMEA are achieved by expert groups to predict whether failures in a system can cause relevant effects on the behavior of a system. For this task three types of information are required: the knowledge of the considered system behavior, the relevant failure modes, and the effects of interest that are derived from the system requirements. Usually, the component failure modes and system effects are described using natural language or semi-formal expressions which are imprecise by nature and often interpreted differently by different experts. Consequently, such a way to proceed can lead to erroneous or hardly exploitable analysis conclusions. To tackle these issues, we propose a template for safety analysis. This template contains the needed information (description of the system behavior, component failure modes, and tracked effects) described using formal languages. The use of a formal knowledge representation makes the results of the FMEA independent from the analysis authors and thus repeatable. Besides this, the template also supports formalizing and documenting the assumptions and hypotheses made to reach the conclusions of an FMEA. The practical use of such a template for safety analysis is highlighted through the safety analysis (single point of failure) of a voltage monitor presented in the “ARP4761 recommended practice for aerospace system safety assessment”. The analysis of the voltage monitor is performed automatically by a program that uses the information contained in the template. The FMEA results of the ARP4761 and those obtained using the template are then compared. The interest of the proposed template for automated safety analysis is discussed and further work to be achieved on the template is concluded.