<title>Graphical user interfaces for heterogeneous distributed systems</title>

Abstract

In modern object-oriented computer systems the internal state of the entire system consists of the internal states of many objects, probably distributed over a heterogeneous network of computers. The man machine interaction in such an application is based on the visualization of states on one hand and the modification of states in combination with event generation on the other hand. This paper describes concept and realization of a reusable service for general man machine communication.Keywords: graphical user interface, data visualization, service, object-oriented service OVERVIEWThis research arises from a cooperation with the IEEE task force on ECBS and has two main goals: First, to find a common standard for the process of creating large computer systems and second to define standards for reusable software components, the "services". A service is designed to solve a given problem by processing tasks and results. With a given communication platform it is possible to place the services on different hardware systems independent of the specification. This is realized by distributed objects for heterogeneous systems (Figure 1).Three basic types of services can be distinguished: The system services are needed for communication and process scheduling. The basic services are located above the system service. At this point of time, there are a layer for man machine interaction, for measurement and control and a database system for persistent data. The third type of service is application dependent, which means, that these services are build for a special solution, whereas the other ones only have to be configured for a given task.One of the most important services is the man machine interaction. The task of any man machine service (MMS) is to inform a human user of a system's state and to allow modifications of this state. Due to the fact that man can perceive and handle information fastest in a visual way, this is the best channel to inform about complex system states. The optical channel is also a good choice to support human interaction. This is achieved in feeding back the user's actions. A MMS has to provide two general functions:

Design of distributed real time systems in process control applications

“…For man-machine-interactions a highly configurable, easy to use service is necessary to prevent the developer from writing special solutions for every task [BSV195,BSV295,BSV395]. These service offers an application programming interface independent from the underlying graphics hardware and screen resolution.…”

<title>Flexible dynamic models for user interfaces</title>

“…For this reason, we have introduced two models in our system Fluids to define the user interface. 5 The static model describes the user interface structure, using the design and placement of their components. 6 The idea of symbolic information visualization is consequently used: Menus are aggregate symbols, composed of buttons, which are symbols too.…”