Of course, there will be cases when the product concept is found to be seriously off the mark and must be altered. These cases should be rare and will require that the entire plan for the project be renegotiated. The responsibility for spotting these occasions rests with management, and developers should be clear that their job is to focus completely on the project as described, not to watch the market for reasons to alter that plan. Management then must assume the burden of watching outside the team's restricted field of vision for broader events that could upset the project. Finally, be persistent about supporting the required changes.
People look for a chance to return to the comfortable practices of the past.
Make it clear that this is not an option. Your constancy of purpose will affect everyone else. Although upper management may sincerely believe in the value of faster cycle time, it may flinch at changing accustomed patterns of business, especially its own patterns. Team members took the initiative and, since they had all the marketing, purchasing, engineering, and manufacturing expertise right on their team, wrote a product specification. They then issued the specification under a cover memo, saying that they were ready to start designing and would consider the specification final unless they heard objections within a week.