Designing for Flex – Part 4: Merging the web and the desktop

Moving to the desktop

Most desktop applications can be classified into one of two types, sovereign applications and transient applications (Alan Cooper and Robert Reimann developed this distinction in their excellent 2003 book, About Face 2.0). Sovereign applications fully consume the user’s attention for fairly long periods of time. They are usually best used in full-screen mode, they contain a wide variety of tools and features, and they support many different tasks. Many sovereign applications are creation applications, although this is not exclusively true. Examples include Adobe Photoshop, Microsoft Word, and Intuit TurboTax.

Figure 12. Adobe Flex Builder is an example of a sovereign desktop application. Note the extensive use of small icons, multiple views of information, and the large number of functions available at one time. Sovereign applications are designed to absorb the user’s attention for long periods.

Transient applications, on the other hand, are opened and used only briefly for a small number of fairly short tasks. Users rarely use them in full-screen mode since they generally share screen space alongside sovereign or other transient applications. Examples include Microsoft Windows’ Calculator, most Apple Dashboard widgets, and desktop display preferences dialogs. Some transient applications may also have sovereign modes, for example, Apple iTunes is transient while listening to music in the background but also has sovereign aspects since many users spend time using it to organize and import their music.

Figure 13. Adium, an instant messaging client, is an example of a transient application. Users spend little time in the environment and tend to hop in and out, so there are few controls and functions. Transient applications are designed to be used occasionally and/or sporadically.

Sovereign and transient applications should be designed quite differently. Since sovereign applications monopolize users’ attention, they can consume more screen real estate, use smaller controls, and employ more complex and involved (but still useable and desirable) interactions. Transient applications must keep interactions simple and focused around the few tasks the application supports. Controls must be large and clearly distinguishable. Since users come to the application infrequently, they will not spend time finding fiddly little user interface elements; all tasks should be immediately and transparently obvious.

Think carefully about these two categories before designing your application. Consider the user goals, content, and tasks you must support before choosing an application type. Many AIR applications will be transient applications, and transient applications are designed quite differently from the large sovereign applications that most designers and developers think of when they imagine a desktop application.

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