Dialogue design implications of task allocation between man and computer

Abstract

It is argued that the form of dialogue required in man-computer interaction is dependent upon the nature of the task and the allocation for task functions between man and computer. The paper examines the design implications of two task variables; task openness and task frequency. It concludes that one of man's essential roles in the operation of man-computer systems is to cope adaptively with the openness in the system and that one of the problems of current systems is that they infer a closed model of the task that may inhibit the user in his efforts to provide an adaptive contribution.

The paper considers the kinds of constrained languages appropriate for closed tasks and the command languages necessary to make flexible and powerful use of computer facilities when the task is open. It raises the dilemma of the infrequent user with open-ended tasks who needs a complex formal language but is unwilling or unable to master it. A number of solutions are offered to this dilemma. Finally, a plea is made for the development of task analysis methods which attempt to assess openness in order that designers do not assume tasks exhibit a greater degree of closure than is found in practice.