H7 Flat And Narrow Tree *

WorldBeat, whose menu tree is shown in the opening picture, consists of a start page that explains briefly what the exhibit is about, and how to use the batons, and then leads to a main selection screen where the user can choose one of the six WorldBeat components, go back to the start page, or read the credits for the system. The component pages in turn offer one or more choices to continue further into the respective component, or return to the main selection screen.

The Interactive Fugue exhibit has a similar overall structure. The initial selection page leads to four subpages for its various features, which in turn lead the user through a sequence of subsequent pages to use those features.

The hierarchical organizing principle is ubiquitous in electronic systems and user interfaces. It is at the heart of the directory structure of the file system of all major operating systems, and replicated in their graphical "folder" view of the file system. It is also a general user interface pattern described by Tidwell [1998] as HIERARCHICAL SET.

If the hierarchy is kept small enough, the current position can be remembered well, and the navigation metaphor be used confidently, even by computer novices. A commonly quoted maximum capacity of human short-term memory and processing is around seven chunks of information [Miller, 1956], so this is both a good estimate for an upper limit on the number of entries from which the user can choose at each level. The maximum path length should be even shorter to avoid people forgetting where in the tree structure they are.