12.2 The Golden Rules and the ISO Norm 9241

Complex statistical tasks require more and more complex statistical programs. In consequence more complex user interfaces are needed to be developed. Software developers recognized that common rules exist in simplifing the use of software systems. [24] published a summary of these rules known as the ''golden rules'' of user interface design:

1. Achieve consistency
   The first rule is the one which is most often violated, especially when teams of people work together. Users expect that in similar situations the software behaves similarly and requires the same actions from the user.
2. Use shortcuts
   Beginners need a comfortable clear structured way to accomplish their task, but power users of a software package want to do their work as quickly as possible.
3. Give informative feedback
   Users need to have a feedback on their actions. The amount of the feedback depends on the action and the user's experience. Frequent actions require only short answers whereas rare actions require more extended answers. Beginners need more feedback whereas power users may just need acknowlegdement that the task is finished.
4. Design closed actions
   Actions should have a clear structure with a start and a well-defined end. This holds especially for dialogs and forms.
5. Offer error prevention and easy error handling
   Software should not support erroneous input from the user and provide default values. The user should be able to recover easily from errors. If a user can revert his actions easily then this will increase his trustworthiness in the software package.
6. Support user control
   Users prefer to initiate actions in a software package. If a user believes that he only reacts to the system he will experience a control loss.
7. Reduce memorization
   Humans can only remember seven plus minus two information bits in their short term memory [17]. Extensive memorization to handle a software package should be avoided.

A formalization of the rules can be found, partially in very detailed instruction, in the ISO (International Standardization Organization) norm 9241. The norm itself, which distinguishes between requirements and recommendations, consists of 17 parts:

1. General introduction
2. Guidance on task requirements
3. Visual display requirements
4. Keyboard requirements
5. Workstation layout and postural requirements
6. Environmental requirements
7. Display requirements with reflections
8. Requirements for displayed colors
9. Requirements for non-keyboard input devices
10. Dialogue principles
11. Usability statements
12. Presentation of information
13. User guidance
14. Menu dialogs
15. Command dialogs
16. Direct manipulation dialogs
17. Form-filling dialogs