Designed for Use, 2nd Edition

Chapter 30 Designing the Back End

In Chapter 11, ​ The Mental Model ​, we talked about three different kinds of models:

• The mental model is how users think the product works.

• The UI model is how the product is presented to the users in the user interface.

• The implementation model is how the product is implemented.

In that chapter, I made the point that the users’ experience is optimal when the three models—how the users expect a product to work, how the product presents itself, and how the product actually works—are all as close to each other as possible. In a perfect world, the three models would be completely consistent, and users would ...