Human Interface Guidelines: The Apple Desktop Interface

Metaphors from the real world

Use concrete metaphors and make them plain, so that users have a set of expectations to apply to computer environments. Whenever appropriate, use audio and visual effects that support the metaphor. Most people now using computers don't have years of experience with several different computer systems. What they do have is years of direct experience with their immediate world.

To take advantage of this prior experience, computer designers frequently use metaphors for computer processes that correspond to the everyday world that people are comfortable with. The desktop itself is the primary metaphor for the Apple Desktop Interface. It appears to be a surface on which users can keep tools and documents. Yet many of the elements of the Apple Desktop Interface don't have a clear physical counterpart. For example, scroll bars clearly belong to the computer domain; they only loosely resemble real scrolls. And pull-down menus aren't much like real restaurant menus, except in providing the opportunity to make choices from alternatives.

The desktop, then, is an inviting metaphor that provides easy access to the system. Other metaphors, especially when consistent with the desktop, can fit into the system. Once immersed in the desktop metaphor, users can adapt readily to loose connections with physical situations—the metaphor need not be taken to its logical extremes.