ABSTRACT

The design of user interfaces for any kind of interactive systems includes two major areas: (1) design of functionality and (2) interaction design. To find the right systems objects and operations is the core task of human-centered automation in process control. (Woods 1996; Billings 1997; Moray 1999). Interaction design covers such tasks as design of displays and controls, and dialogue design (Moran 1981; Nielsen 1986). Human-centered design of functionality principally aims for an optimal level of psychophysiological demands, with neither too low demands (leading possibly to monotony and boredom) nor too high strain (leading possibly to stress). However, human-centered design of interaction aims for a minimal level of demand. Users or operators should work on the task, but in the best case they should not realize that they are using an computer in doing this. Concepts such as the invisible computer (Norman 1998), seamless interaction (Ishii and Ullmer 1997), and calm computing (Brown and Weiser 1997) indicate the tendency to minimize the demand resulting from interaction. While coping with complexity caused by functionality can be regarded as challenging, coping with complexity caused by interaction is frustrating (Table 1).