Stages of User Activity Model as a Basis for User-System Interface Evaluations

Abstract

This paper discusses the results of the first phase of a research project concerned with developing methods and measures of user-system interface effectiveness for command and control systems with graphical, direct manipulation style interfaces. Due to the increased use of prototyping user interfaces during concept definition and demonstration/validation phases, the opportunity exists for human factors engineers to apply evaluation methodologies early enough in the life cycle to make an impact on system design. Understanding and improving user-system interface (USI) evaluation techniques is critical to this process. In 1986, Norman proposed a descriptive “stages of user activity” model of human-computer interaction. Hutchins, Hollin, and Norman (1986) proposed concepts of measures based on the model which would assess the directness of the engagements between the user and the interface at each stage of the model. This first phase of our research program involved applying three USI evaluation techniques to a single interface, and assessing which, if any, provided information on the directness of engagement at each stage of Norman's model. We also classified the problem types identified according to the Smith and Mosier (1986) functional areas. The three techniques used were cognitive walkthrough, heuristic evaluation, and guidelines. It was found that the cognitive walkthrough method applied almost exclusively to the action specification stage. The guidelines were applicable to more of the stages evaluated but all the techniques were weak in measuring semantic distance and all of the stages on the evaluation side of the HCI activity cycle. Improvements to existing or new techniques are required for evaluating the directness of engagement for graphical, direct manipulation style interfaces.