Ultimately somebody involved has to make the decision of what is needed. The customer often doesn't know exactly what they need and even more often does not kno

Ultimately somebody involved has to make the decision of what is needed. The customer often doesn't know exactly what they need and even more often does not know what is realistic. The developer often doesn't understand the problem(s) and even more often has little idea of why the customer is doing what they are doing. There really is no substitute for having someone (or a team) study the area in detail who has the background to be able to understand the problem(s) and is able to translate this understanding into a development plan. For anything but the most trivial problems this requires a large investment in time, money and effort.