The seven-stage structure can be a valuable design aid, for it provides a basic checklist of questions to ask to ensure that the Gulfs of Evaluation and Execution are bridged.
How Easily Can One:
- Determine The Function of the Device?
- Tell What Actions Are Possible?
- Tell if System is in Desired State?
- Determine Mapping from Intention to Physical Movement?
- Determine Mapping from System to Interpretation?
- Perform the Action?
- Tell What State the System is In?
... On the whole, the questions for each stage are relatively simple. And these, in trun, boil down to the prionciples of good design (introduced in chapter 1).
- Visibility. By looking, the user can tell the state of the device and alternatives for action.
- A good conceptual model. The designer provides a good conceptual model for the user, with consistency in the presentation of operations and results and a coherent, consistent system image.
- Good mappings. It is possible to determine the relationships between actions and results, between the controls and their effects, and between the system state and what is visible.
- Feedback. The user receives full and continuous feedback about the results of actions.
