A good example of a visual metaphor is the directory structure of a computer. While the computer actually stores files and data haphazardly on its hard drive, the visual metaphor presented to the user is that of file folders and a vertical ordering system. This metaphor gives an artificial but clear sense of order to the system. As users we imagine that our documents are being held in these little folders, and that there is some kind of depth to them. Mental models and metaphors, however, are still subject to short-term memory restrictions.
Most users begin to get lost when their model contains more than three layers or paths.
At this point, most users will still have a clear understanding of where they are in the program, and how to retrace their steps, if necessary. But if they are again presented a link for more information, such as a case study from within the More Information section, they will begin to lose track of their location or the relationship of the onscreen content to the overall lesson. A simple way to relieve the burden on users' memory is to provide multiple ways to locate and access the content. Common methods are described below. The primary access point is always the program's main menu, which should be well organized and descriptive.