UML Distilled: A Brief Guide to the Standard Object Modeling Language, Second Edition

Transition

The point of iterative development is to do the whole development process regularly so that the development team gets used to delivering finished code. But some things should not be done early. A prime example is optimization.

Optimization reduces the clarity and extensibility of the system in order to improve performance. That is a trade-off you need to make— after all, a system does have to be fast enough to meet users' requirements. But optimizing too early makes development tougher, so this is one thing that does need to be left to the end.

During transition, there is no development to add functionality, unless it is small and absolutely essential. There is development to fix bugs. A good example of a transition phase is that time ...