Convenient Environment Actions

Examples:

Power switches
Pausing or resuming a video game
OK / Apply / Cancel buttons on dialogs
Minimize / Maximize / Quit buttons on Windows application frames

Bad Examples:

Applications in which the only way to gracefully quit is an item on a long "File" menu
Macintosh power switches that were next to CD-ROM drives, making them look like "Eject" buttons
Windows 95 logout command, which is found first under "Start", then under "Shutdown"

Context: The user can take actions that affect the existence or state of the whole artifact. This is necessary in countless artifacts, with the exception of physical things like books or charts, in which those actions are absent or implicit.

Problem: How should the artifact present these actions?

Forces:

The user should know exactly how to stop or leave this artifact at any time.
The user should know what other actions are available.
The user may already know what they have to do, but they need to find the corresponding action.
The user may need to perform these in a hurry, or under stress.
Doing these actions accidentally may be disastrous.

Solution: Group these actions together, label them with words or pictures whose meanings are unmistakable, and put them where the user can easily find them regardless of the current state of the artifact. Use their design and location to make them impossible to confuse with anything else. Set them up so they are not easy to trip accidentally -- hardware devices can use physical barriers to do this, but software's more difficult. Confirmation dialogs are clumsy but somewhat effective; use them until someone invents something better. If a state change or shutting down can cause disaster, at least try to make the effects reversible. Disable state-change actions whenever they become irrelevant or impossible (Disabled Irrelevant Things), but never do this to controls that close or quit the artifact.

Resulting Context: Icon buttons are often used for these. As long as familiar symbols are used, they work well; use the standards for the artifact's intended domain and culture. ("X" for quit, "?" for help, check-mark for OK, and 0/1 for off/on are common ones.) When the icons for these basic functions are incomprehensible, or if you hide them in an unexpected place, the user has to carry a heavier memory burden.

Notes: Is this whole pattern just a consequence of clumsy design in the first place? Something about the "books and charts" comment in the Context makes me think about the necessity of explicit Environment Actions in software and electronics. If we could design these so well that they no longer need explicit commands for on/off, save state, change mode, etc., then we might get truly dramatic gains in usability. I don't know how to do this, of course. If I did, I would be off designing things that way, not writing this pattern.

Comments to: jtidwell@alum.mit.edu
Last modified May 17, 1999