Most software engineers have heard about the V Model, and it serves as basis for the structure in the safety standards. The V Model well suited for the dedicated software development in the context of a specific system. However, our experience has shown that the V Model causes confusions when considering the risk assessment and mitigation of properties of pre-existing software elements that are integrated into a system context after its construction. Hence, there is the need to introduce the Z Model, which may resolve that confusion.
