However, metaphors can also restrict users expectations of what is or isn't possible. Click here for a quick test of the suitability of a metaphor . Provide feedback at all times. The application should provide feedback to help users diagnose problems. Design for Error.
Error messages are often the best clue to what has gone wrong in case of a breakdown situation.
Ensure that the error messages are consistent with the design model, that they are intelligible, that they cover all potential reasons for the breakdown, and that they suggest recovery actions. Follow this link for an example of an error message .