Approximately 25 yr ago, the first computer-based process control systems, including computer-generated displays, appeared. It is remarkable how slowly the human-computer interfaces (HCI's) of such systems have developed over the years. The display design approach in those early days had its roots in the topology of the process. Usually, the information came from the piping and instrumentation diagrams. Later, some important additional functions were added to the basic system, such as alarm and trend displays. Today, these functions are still the basic ones, and the end-user displays have not changed much except for improved display quality in terms of colors, font types and sizes, resolution, and object shapes, resulting from improved display hardware.

Today, there are two schools of display design competing for supremacy in the process control segment of the HCI community. One can be characterized by extension and integration of current practice, while the other is more revolutionary.

The extension of the current practice approach can be described in terms of added system functionality and integration. This means that important functions for the plant operator - such as signal validation, plant overview information, safety parameter displays, procedures, prediction of future states, and plant performance optimization - are added to the basic functions and integrated in a total unified HCI for the plant operator.

The revolutionary approach, however, takes as its starting point the design process itself. The functioning of the plant is described in terms of the plant goals and subgoals, as well as the means available to reach these goals. Then, displays are designed representing this functional structure - in clear contrast to the earlier plant topology representation. Depending on the design approach used, the corresponding displays have various designations, e.g., function-oriented, task-oriented, or ecological displays.

This paper gives a historical overview of past developments and describes, in terms of examples, the current state of the art in HCIs for process control - as well as the newer HCI directions.