Dynamic Descriptor **

The Mac OS® operating system uses icons with names to represent files, folders, disks, printers, and many other objects in its user interface. However, even experienced users occasionally need some basic information about an object, for example to find out what application created a certain file. Referring to printed documentation, or even to an online manual, would interrupt the task too much. Displaying all this information for every visible object all the time would clutter the screen. The solution introduced by Apple is called "Balloon Help", and it shows a short description in a bubble next to any item that the mouse pointer touches. This feature needs to be switched on explicitly, because it creates a certain visual disturbance, and the average user, who has already gained some experience with the system, does not even want to see this information appear dynamically everywhere she points.


Figure: Mac OS® Balloon help, explaining an object under the pointer on-screen.

Microsoft Windows® features a similar mechanism called "ToolTips". The general pattern has been identified by Tidwell [1998] as SHORT DESCRIPTION, and the INTERACT patternsworkshop [Borchers et al., 2001] used a similar pattern, DESCRIPTION AT YOUR FINGERTIPS, as stand-alone example of a typical HCI design pattern.

The situation in interactive exhibits is different, however: the typical user is a first-time, one-time user. He has no experience with the system, and will probably never encounter it again. Therefore, no long-term learning curve development can be assumed, and such dynamic descriptions need to be provided automatically by the system, without requiring explicit user action.

In the WorldBeat exhibit, for example, when a user moves the baton cursor over a selectable item on the main selection screen, the icon fades into the background, and a short explanatory text of lains what the component is about that can be reached via this item (see the opening image). This design allows users to explore what awaits them inside the various components, deciding on what they would like to try first or next, without having to enter all the components to find out what they are about. It adds another, intermediate layer of detail between the opening page and the subsequent component pages.

Other media types can use a similar concept. Voice mailbox systems usually let the user quickly progress through their menus, with short announcements that can be stopped at any time, but when the user remains idle for a while, additional context-sensitive information on the current menu, its options, and use, is frequently played back.