Slide 9.a: XML (eXtensible Markup Language)
Slide 9.c: Why XML?
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XML (Cont.)

XML Is Free and Extensible.
XML tags are not predefined. You must “invent” your own tags. The tags used to mark up HTML documents and the structure of HTML documents are predefined. The author of HTML documents can only use tags that are defined in the HTML standard (like <p>, <h1>, etc.).

XML allows the author to define his own tags and his own document structure. The tags in the example above (like <to> and <from>) are not defined in any XML standard. These tags are “invented” by the author of the XML document.

XML Is a Complement to HTML.
XML is not a replacement for HTML. It is important to understand that XML is not a replacement for HTML. In future Web development it is most likely that XML will be used to describe the data, while HTML will be used to format and display the same data. The best description of XML is this:
XML is a cross-platform, software and hardware independent tool for transmitting information.
XML in Future Web Development
XML will be as important to the future of the Web as HTML has been to the foundation of the Web and that XML will be the most common tool for all data manipulation and data transmission.

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