One of my favorite requirements stories is from the Practical Product Management class that Pragmatic Marketing's Barbara Nelson teaches. She broached a brief discussion on requirements, and the issue of user interface requirements somehow came up. Students in the class disagreed over whether it was appropriate to include user interface design details in market requirements.
One of the students confidently stated, "If the customer tells me he wants the button to be blue, then that's the requirement. Period."
The student thereby boiled two important issues down to one statement:
1. Is a user interface design detail a requirement?
2. Should a requirements analyst passively accept customer specifications?
Readers of my blog know that I answer "no" to both of these questions. The requirements analyst should ask, "Why?" I.e. what problem will the blue button will solve? The process is actively facilitative and gets beyond design details to the root of the customer's concerns.