还是系统集成的一个作业。
背景： 作为计算机世界，很多领域独立发展，归根到底，很多时候都是和数据打交道，那么现有的这么多系统如何交换数据就成为一个问题？
解决方案：XML（以后可能还会有更好的吧，目前就是它了）
What is XML?
XML is a markup language for documents containing structured information.
Structured information contains both content (words, pictures, etc.) and some indication of what role that content plays (for example, content in a section heading has a different meaning from content in a footnote, which means something different than content in a figure caption or content in a database table, etc.). Almost all documents have some structure.
A markup language is a mechanism to identify structures in a document. The XML specification defines a standard way to add markup to documents.
资料：
http://skew.org/xml/
http://skew.org/xml/stylesheets/treeview/
http://www.cranesoftwrights.com/resources/showtree/