Explaining Embedded Software Modelling Decisions

As today's devices, gadgets and machines become more intelligent, the complexity of embedded software controlling them grows enormously. To deal with this complexity, embedded software is designed using model-based paradigms. The process of modelling is a combination of formal and creative, design steps. Because of the partially non-formal character of modelling, the relation between a model and the system cannot be expressed mathematically. Therefore, the modeller's justification that the model represents the system adequately can only be non-formal. In this paper we discuss the nature of non-formal modelling steps and pin-point those that create a 'link' between the model and the system. We propose steps to structure the explanation and justification of non-formal modelling decisions. This in turn should enhance confidence that the non-formal, physical world surrounding the embedded system is adequately represented in the model.