A user interface design specifies the operation logic and layoyt of each screen. It is difficult to evaluate the time it took to desing a user interface just by looking at it. On the contrary, when you see a great user interface, it is self-evident. But creating one requires.
The sooner you start to code, the longer the project will take.
- allows own workers to work on business critical issues
- avoids costly changes later in the development process
- produces a great user experience
When the requirement specification is complete and the target user group and environment is known.