“Plan-driven development works well if you are applying it to problems that are well defined, predictable, and unlikely to undergo any significant change. The problem is that most product development efforts are anything but predictable, especially at the beginning. So, while a plan-driven process gives the impression of an orderly, accountable, and measurable approach, that impression can lead to a false sense of security. After all, developing a product rarely goes as planned. For many, a plan-driven, sequential process just makes sense, understand it, design it, code it, test it, and deploy it, all according to a well-defined, prescribed plan. There is a belief that it should work. If applying a plan-driven approach doesn’t work, the prevailing attitude is that we must have done something wrong. Even if a plan-driven process repeatedly produces disappointing results, many organizations continue to apply the same approach, sure that if they just do it better, their results will improve. The problem, however, is not with the execution. It’s that plan-driven approaches are based on a set of beliefs that do not match the uncertainty inherent in most product development efforts.”