Time affordances: the time factor in diagnostic usability heuristics

A significant body of usability work has addressed the issue of response time in interactive systems. The sharp increase in desktop and networked systems changes the user's focus to a more active diagnostic viewpoint. Today's more experienced networked user is now engaged in complicated activities for which the issue is whether the system is carrying out the appropriate task and how well it is proceeding with tasks that may vary in response time from instantaneous to tens of minutes. We introduce the concept of a time affordance and a set of principles for determining whether the diagnostic information available to the user is rich enough to prevent unproductive and even destructive actions due to an unclear understanding of progress.