Time I saw a blog (http://martinfowler.com/bliki/principlesofxp.com/bliki/principlesofxp.html) of Martin Fowler, introduced things about Principles. It is deeply, in fact, the key to XP is not XP is an attitude, some principles, that is, the so-called "non-view". And these are non-viewing in a relatively high level is Value, which is reflected in the middle level is Principles.
In terms of practice, it should be an extremely beneficial practice of team building, but it is difficult to implement. Automatic test actually controls the rhythm of the entire XP, and the control of "route" is critical. Refactoring is undoubtedly the best way to understand the beauty of the design. Continuous integration is a useful practice for team development.
