Donald A. Norman Rule

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  The Donald A. Norman rule is a set of design principles for creating user-centered products and interfaces. The main points of the rule are:                                                                                                       
• Visibility: The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.                                                                                                  
• Feedback: The system should always provide appropriate and informative feedback about the results of the user's actions.                                                                                                                                         
• Constraints: The system should be designed to guide the user towards the right action, rather than relying on the user to remember the right sequence of actions.                                                                       
• Mapping: The relationship between controls and their effects should be simple and consistent, so that the user can understand how to operate the system.                                                                               
• Simplicity and consistency: The system should be designed to be simple and consistent, so that the user can learn to use it quickly and easily.                                                                                                      
• Error management: The system should be designed to minimize the likelihood of errors and to recover from them gracefully.                                                                                                                           
• Flexibility and efficiency: The system should be designed to allow the user to work in their own way, at their own pace, and to provide shortcuts for experienced users.