In this paper we present a national project located in the area of computer aided testing and certifying (CATC) of physical devices. The aim of this project is to develop an Information System that supports the various activities of different user groups in a German federal institute of weights and measures. We decided to use the formal object oriented specification language \trol1 throughout the project. Our purpose is to provide a method which is based on a formal specification language to design a complex information system.