ABSTRACT
In this chapter we discuss a methodology appropriate for interface design, which we define as the process whereby the designer plans and specifies the user interface. The interface designer’s objective is to make devices easier and more enjoyable to use, and to make it possible for people to perform tasks which they might not otherwise be able to accomplish. With this objective in mind, we will propose a guiding interface design principle and offer a methodology for applying this principle to different interfaces. We would like to stress at the outset that ours is a methodology under development and that it needs additional empirical support. This approach to interface design is worth considering because it is empirically based, potentially formal, and in concert with current thinking in cognitive science. It is, of course, up to the reader to decide whether or not the arguments and data presented are sufficient to justify such optimism. In the following sections we first discuss some common approaches to interface design in order to place our methodology in perspective. We then present the theoretical motivations for our approach, along with a related discussion of scaling and knowledge acquisition techniques, followed by a review of several applications that illustrate key aspects of our methodology. The last of these studies is an ongoing investigation of UNIX users aimed at improving the on-line documentation system.
