Abstract

Introduction and Overview At the beginning it was just a vision. A vision with many different facettes like electronic textbooks with integrated active elements, a versatile platform for the use and design of expressive graphical user interfaces and a new paradigm of how to look at software that is based on completely autonomous functional units, so--calledend--user objects. The vision was still rather diffuse when we turned it into a project, and it was by no means clear, if this was really just one project or actually a series of more or less independent projects. Among the few more concrete aims, let us pick the crucial topic "separation of application and user interface programming". The principle we had in mind is simple. It is illustrated in Figure 1 with the example of the simulation of a waiting line. The essential point here is that the application program (the simulator) is kept absolutely independent of any kind of display (the panel) because it ope

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