A substantial portion of the two interface design courses I taught at the University of Illinois this semester involved interface design evaluation. I divided students into small groups and asked them to review an existing interface. As a result of these exercises, we gradually developed an informal set of criteria for evaluating effective designs:
Does the interface provide contextual information about: where you are situated within content (the information and activities that constitute an interactive system), the various relationships between content, and a big picture (macro view) of the information/interaction space?
Anticipation is closely related to context and refers to the ability of an interface to answer user questions before they need to be asked. Does this interface anticipate what I’d like to do and provide adequate and appropriate interactions and information?
Though being consistent when presenting information and interactions sounds relatively easy, the truth is it’s difficult enough to be the most common problem in interactive systems.
Does the interface get in the way of your interactions or is the content (information/activities) the focus?
Many interface designs are a delicate between visual simplicity and information density: offering many choices/options vs. guiding users without overwhelming them. Which side you lean toward depends on your target audience. However, a clear presentation of information (aesthetic integrity) is always a must.
If metaphors are utilized to clarify the system are they limiting or empowering?
Do user actions result in clearly presented system reactions? Is what you see really what you get?
Who’s in charge: you or the system?
Are user needs and objectives the driving force for the design? How well do the designers know their users?
Of these, the vast majority (Context, Consistency, Transparency, Clarity, Feedback, Metaphor, User-Focused) are issues of communication. What are you telling your audience and how are you saying it? And because most interfaces are highly visual, we’re really dealing with issues of visual communication.