Skipping both the content model and the navigation map proved to be a mistake, and we later needed to go back to complete the navigation map before we could finish the design. The problem is that, without a navigation map showing all the screens, pages, windows, and dialogs and how they are interconnected, you have no overview of how everything fits together. Without this picture of the architecture, you make too many mistakes in placing particular features. Once we completed the navigation map and validated it with our users and domain experts, the design process got back up to speed. Prototypes We also learned some lessons about using prototypes.
Prototypes have many uses.
At their worst, they can end up being shipped out as a hacked and patched substitute for a real product. In crunch-mode projects, prototypes can be a costly diversion of resources. One problem is that prototypes are made to be thrown away, whether in whole or in part. Prototypes can allow you to get something working quickly, but don't be seduced into thinking that building prototypes will save you time. When you are caught in a time crunch, prototypes can become a major time sink.