In yesterday's entry, I listed some factors that can indicate an organization's excessive emphasis on functional requirements. I also mentioned that this overemphasis has a negative impact on product development. Why?
For example, a skilled requirements analyst might specify an ease of use constraint as a limit on the number of user gestures it should take for a user to accomplish a functional goal. A product manager who dips into design might instead describe a user interface, couching the description in a series of functional specifications.
By dipping into design, the requirements analyst has lost sight of the underlying problem the product is supposed to solve or avoid. In the example, she has lost sight of the metric that determines whether the product is easy enough to use. Without such a metric in the requirements, the QA team may test the design but not the real requirement. Product designers will have no leeway to apply their creative expertise. Developers will code to the design without grasping the problems they're trying to solve.