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“If anything can go wrong, it will. ”

“If there’s more than one possible outcome of a job or task,
and one of those outcomes will result in disaster or an undesirable consequence, then somebody will do it that way. ”

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Regardless of the exact composition and origin of the phrase,
its spirit embodies the principle of defensive design
— anticipating the mistakes the end-user is likely to make.

For example, the 3.5-inch floppy disk once used in many personal computers will not easily fit into the drive unless it is oriented correctly.

In contrast, the older 5.25-inch floppy disk could be inserted in a variety of orientations that might damage the disk or drive.

The newer CD-ROM and DVD technologies permit one incorrect orientation: the disc may be inserted upside-down, which is harmless to the disc.

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A defensive designer knows that if it is possible for the disc to be inserted the wrong way, someone will eventually try it.

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— Wikipedia, edited by Me

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2009.01.11 Sunday