If there and no risks whatsoever, use the waterfall model for your development. If there are risks, which is the case in any new development, we have to constantly assess how we are going to control these risks. Development is for an important part risk-reduction. If the development is done, all risks should have been resolved. If a risk turns out for worse at the end of a development, we have no time to resolve it any more. If we assess the risks earlier, we may have time to decide what to do if the risk turns out for worse. Because we develop in very short increments of one week, the risk that an assumption or idea consumes a lot of development time before we become aware that the result cannot be used is limited to one week. Every week the requirements are redefined, based upon what we learnt before.
Risks are not limited to assumptions about the product requirements, where we should ask ourselves:

• Are we developing the right things right?
• When are things right?

Many risks are also about timing and synchronisation:

• Can we estimate sufficiently accurate?
• Which tasks are we forgetting?
• Do we get the deliveries from others (hardware, software, stakeholder responses, …) in time?

Actually the main questions we are asking ourselves systematically in Evo are:

What should we do, in which order, to which level of detail for now.

Too much detail too early means usually that the detail work has to be done over and over again later. May be the detail work was not done wrong. It only later turns out that is should have been done differently.