Safety concept trees. An approach to a formalized depiction of safety concepts for safety-critical systems

The creation of safety critical systems is an expensive and demanding venture. Nevertheless, there is a lack of tools and concepts that assist the developer throughout the whole process of conceiving, designing and testing of safety measures. This thesis introduces the Safety Concept Tree (SCT) approach. A Safety Concept Tree is a formalized and structured representation of a system's safety concept. This concept covers all measures taken to control system hazards, the top-down refinement of the measures, as well as the planning of activities to prove the correct realization of these. Additionally, Safety Concept Trees provide a clear depiction of the coherences and logic dependences among the elements of a safety concept. In sum, the created big picture context facilitates an efficient assessment of the planned safety strategy, as well as its further elaboration. Safety Concept Trees are adaptable to different safety standards, which allows for their use in multiple application areas. Furthermore, the creation of a Safety Concept Tree is governed by a meta-model. This formal foundation provides guidance during the creation of a safety concept and supplies the developed approach with all requisites for a future development of automated analyses. The SCT Builder, a graphical editor for Safety Concept Trees, has been developed over the course of this project and is introduced in the following thesis.