Putting XP into Practise

We have already said that XP is not a design method. Indeed, all it actually is in any formal sense is a set of four values that have motivated twelve practises. Some of these practises are more clearly oriented towards a process than others. For example, the planning game practise, as we will see, has a lot to say about itself. Other practises, such as the 40-hour week are rathermore like guidelines, than a process. That is, you either over work your developers doing 60–80 hours a week or you don't. There is not a lot to say about how you limit the number of hours worked to 40 (exception management buy in and developer acceptance).