Stolen design pattern: diffing

How are things now, and how we they be when I’m done?

Diffing

Verb: compare (files) in order to determine how or whether they differ.

Software developers use it to compare changes made to a file.

Why don’t designers use diffing more often?

Most systems offer a way for administrators to configure a list of settings.

Diffing could help those users confidently make the necessary changes by offering two windows:

1. How are things now?
2. How will things be?

This pattern is close to that seem on many eCommerce websites where the user can compare the item they’re looking at to one or more others.

But there is a key difference: diffing seems most valuable when comparing current and future states of a system. Diffing is not what happens when a user is comparing two future states.