Principles

Values are too abstract to directly guide behavior. Long documents are intended to communicate, so are daily conversations. Which is the most effective? The answer depends partly on context and partly on intellectual principles. In this case, the principle of humanity suggests conversation meets the basic human need for connection and so is the preferred form of communication, all other things being equal. Written communication is inherently more wasteful. While written communication allows you to reach a large audience, it is a one-way communication. Conversation allows for clarification, immediate feedback, brainstorming together, and other things you can't do with a document. Written communication tends to be taken as fact or rejected outright, neither of which is an invitation to increased communication.

The principles listed here are not the only possible principles to guide software development. In the development of safety-critical systems, for example, the principle of traceability is at work. At any time you should be able to trace a path from the work done back to an explicitly expressed need from the users. No work should be done for its own sake. If you work in safety-critical systems, the principle of traceability is important for gaining certification for your systems. Because it is not applicable to all software, I did not include it in this list. Other principles may guide your team's practices, but these are the principles that guide XP.