System Engineering for Development of Requirements and Architecture

Abstract

The ascending branch of the V-model has not always been intensively and systematically implemented in the development process of vehicle components. Crucial indicators for the automobile industry are methods such as statistical design of experiments (DoE) or an intensive validation. The descending area of the V-model has often been neglected. Writing specifications is not strength of automobile manufacturers. As we have previously seen in the architectural views and abstraction levels of architecture, horizontal and vertical interfaces and also other differing views are structuring criteria. This applies particularly to the development of requirements. If we determine functional, technical and logical elements we also need to describe and specify them. If such elements are combined in order to function together as desired and create an intended function, they have to show compatible interfaces that are specified sufficiently. ISO 26262 [1] covers the "specification of interfaces" but does not clearly illustrate the respective requirements. However, the correlation between the work results such as requirement specifications in part 10, are shown based on information flows. In this case only the general abstraction levels system and components are covered and also the differing views on how a system can be described are not covered. Figures 4.1 and 4.2 are published in DIS (Draft International Standard, previous version of the norm) of ISO 26262 part 10 (Figs. 7 and 8). Figure 4.1 was designed for the electronic hardware. It shows the horizontal and vertical interactions and information flows. In the requirements and design phase the direction of the arrow for the vertical axis points from top to bottom. In the integration and test phase it is the other way round. This illustration does not include any iteration in the safety lifecycle, which can become necessary because of model phases, change requirements or verification or validation measures. For the software development one more level is illustrated (Fig. 4.2). It shows an architecture level and a level, which is assigned to the software unit or the design of the software unit.