Please note that the primary purpose of this article is to provide an example of XML in use. There's a great deal of introductory material on the Web about XML, so we're going to go over XML basics pretty quickly. Let's start by discussing why XML is necessary in the first place. It's easy to make the argument that HTML enabled the explosion of the Web. Reading HTML in a Web browser is so simple and intuitive that just about everyone grasps it instantly.
Logical layout makes HTML documents portable.
This provides a great deal of device independence. Hypertext forms webs of knowledge. HTML forms a framework for composite documents. They wanted structured text with some simple outline capabilities, simple hyperlinks, primitive font control, and maybe some pretty pictures and colors, and that's what they created. It was simple, elegant, and useful.