The implementation of system modeling methods in safety engineering

A new scheme for implementing safety activities during system's lifetime and particularly during the concept and design phases has been proposed and utilized in a Weapon System development project. The general need for new schemes comes from the recent experience of the safety engineering community with very complex systems that combine large amount of hardware, software and control elements. Our new scheme is based on coupling new and modern tools that are adopted from Software System Engineering such as the Unified Modeling Language (UML), safety methods of complex systems (STAMP) and classic Risk Management methods to form a convenient safety management system that includes system engineering tools and safety engineering tasks. The scheme takes benefit of the latest trend in Safety Engineering that encourages the use of goal based safety regulations and procedures instead of using strict prescriptive procedures that were common within the safety community until few years ago. An example for the utilization of UML Sequence Diagram tool and Fault Tree Analysis in a detailed analysis of high severity hazard that is associated with the Weapon System is shown. We show that using the scheme helped in the analysis of hazards that are associated with the system and helped to find weak points in the design. An important achievement in utilizing the scheme is the enormous improvement in the communication between the project safety and system engineering functions that helped in implementing important changes in the design very early in the design phase. The utilization of UML tools had a key role in this process. Applying modern system engineering techniques in the safety process increased the involvement of the safety analyst in the detailed product design and apparently brought the safety analyst to have larger impact on the project than the usual role of the safety engineer.