In a previous post, I presented an informal set of criteria for evaluating effective interface designs: Context, Anticipation, Consistency, Transparency Clarity/Simplicity, Metaphor, Feedback, Control, and User-Focused.
Another consideration is Indication. Though closely related to Anticipation and Feedback, Indication is described by Jef Raskin in his book, the Humane Interface, as “highlighting the single object pointed to as the cursor is moved, without any other user action such as clicking.” I prefer a more general definition: indication lets people know when actions or information are available. An underlined hypertext link is a form of indication, as is an indication of the current state in an application. In Raskin’s definition, Indication is a form of Feedback. It provides a response to a change in cursor position (thereby reducing errors) and can be very useful in “cramped” situations where screen space is tight. In the broader definition, Indication is a form of Anticipation. It helps answer user questions before they need to be asked. Can I click on that interface element? What will happen if I do?
I mentioned that most of the design criteria I laid out previously were issues of communication. Indication is no different. According to Raskin: “Indication is necessary if an interface is designed in accord with the principle of visibility.” So once again we encounter the need for effective visual communication in interface design.