As the complexity of production plants and factories grows, the complexity of the corresponding automation systems grows correspondingly. And therefore the size and the degree of interconnectivity of the software grows. For these reasons, the automation domain now encounters the same problems other domains such as avionic, telecommunication, or automotive have experienced before: The number of software problems and bugs does not grow proportionally with the software size. Instead, after a certain software size, software becomes a problem in its own right. And consequently, the automation domain applies similar solution strategies: model-based design on the system level, software component methods, or standardizations of software layers and platforms. This paper presents a new modeling approach which supports both model and software reuse: The Plant Signal Abstraction Layer