Design for Interaction  

If you're familiar with the term user-interface (UI) design, you may think of it as the domain of software engineers. But software isn't the only product that has an interface - all products do, in fact. If you're one of the many designers who creates Web sites, PDF files, or other types of nonlinear or interactive publications, you can probably benefit from some of the principles of UI design.

Mullarky, Rick. Adobe Magazine (1998). Design>User Interface>Interactive