用户故事包含三大部分：卡片，交流和确认

        • 极限编程5原则：
                ○ 快速反馈 Rapid Feedback
                ○ 假设简单Assuming Simplicity
                ○ 增量变化 incremental change
                ○ 拥抱变化 embrace change
                ○ 高品质产品 doing Quality work
        • 极限编程涉及以下实践
                ○ Small release
                ○ The planning game
                ○ Refactoring
                ○ Testing
                ○ Pair programming
                ○ Sustainable pace
                ○ Team code ownership
                ○ Coding standard
                ○ Simple design
                ○ Metaphor 隐喻
                ○ Continuous integration
                ○ On-site customer
        • 用户故事包含三大部分：卡片，交流和确认

产品backlog和sprint backlog： 在Sprint开始的时候Scrum团队从产品Backuplog中把足够的项目放到Sprint backlog上，下一轮迭代开发实现。