Abstract
It is suggested that the most important concepts in defining the form of software's user interface are conceptual models and metaphor. Conceptual models are the form in which capabilities are presented to the user. Conceptual models can be artificial or metaphorical. A conceptual model is artificial to the extent it is based on engineering decision. Metaphors are important to software design because they evoke a connection in the user's mind between the functions of the software and the user's knowledge in a natural way. There are two kinds of metaphor in software design: familiar metaphors and transporting metaphors. Most computer metaphors, like the desktop metaphors, make something familiar to the user, but do not aid functionally. The most important type of computer metaphors are transporting metaphors of which the computer spreadsheet is the archetypal example.<>