Modeling train control systems with Petrinets-an operational specification

European cooperation and new technologies have an effect on the process of requirements specification in the development of train control systems. The meaning of requirements specification under these circumstances and aspects of the system which have to be described in it are discussed. With the goal of achieving a complete behavior specification in a methodically efficient manner, a modeling approach to the recording and description of the relevant aspects is introduced. The approach is based on the use of coloured Petri nets as a formal notation allowing formal analysis. Using the case example of a decentralized level crossing control system, the operational view and its model representation are explained. This view is consistently extended across the technical concept of the system by systematic refinement of the model. Not only the regular technical events realizing the operational requirements, but also alternatives occurring by system malfunction are taken into account. Furthermore, operational events which deviate from the regular course of behavior are integrated, so that the produced model leads to a closed illustration of the permissible system behavior from an operational view in reference to its technical conception