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15. RESPONSIVENESS
15.1 General guidelines for responsiveness
Provide feedback on user actions. Proper feedback gives confirmation to the user that
• the system has detected the user action
• there is a process going on
• the process has ended
It is very important that feedback be provided for processes that last for a period that the user may find annoyingly
long. The feedback must not block other user activity.
15.2 Response time
- For the user to feel as if the program's response is instantaneous, the UI ought to react within 0.1s. In these cases,
a simple graphical feedback, with or without sound, is often adequate.
- The maximum length of an interruption, on average, that the user can tolerate is approximately 1 second. If you
exceed this, you may break the user’s concentration and potentially frustrate him or her. Therefore, things like
redraws, or drawing of dialogs that a user will encounter mid-flow, ought to happen well within this limit.
- For these cases, an Information Banner or Flashing Note can be used.
- 10 seconds is the utmost limit that the user's attention can focus on a dialog. Any longer than this and users will
want to perform other tasks while the process is going on. Therefore:
- make sure the progress indicator gives the user an indication of how long the task will take
- wherever possible, and definitely above this limit, try to make the progress indicator non-modal. Use progress
messages in the background like in the Web browser. Note that the feedback on time-to-completion becomes
even more important if the response time is highly variable, since users will not know what to expect. Users
should be allowed to cancel processes that take long periods of time.
- Suitable notes for these purposes are:
- a Cancel Note with animation or Progress Bar
- Progress Ball
There are two kinds of response time:
- System response: command activation can be emphasised by graphical and/or audio feedback. Use Information
Banners when the use of notes would be too excessive and annoying (see chapter 9).
- Delay caused by transmission: when the delay is caused by the transmission, the UI must
- provide a note about the delay
- inform the user of the reason for the delay
- allow the user to cancel the operation
- provide audio feedback on the progression
- Display an animation (optional)
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