What is XML

* XML stands for EXtensible Markup Language
* XML is a markup language much like HTML
* XML was designed to carry data, not to display data
* XML tags are not predefined. You must define your own tags
* XML is designed to be self-descriptive
* XML is a W3C Recommendation

The Difference Between XML and HTML

XML is not a replacement for HTML.

XML and HTML were designed with different goals:

* XML was designed to transport and store data, with focus on what data is.
* HTML was designed to display data, with focus on how data looks.

HTML is about displaying information, while XML is about carrying information.
XML is Just Plain Text

XML is nothing special. It is just plain text. Software that can handle plain text can also handle XML.

However, XML-aware applications can handle the XML tags specially. The functional meaning of the tags depends on the nature of the application.
With XML You Invent Your Own Tags

The tags in the example above (like and ) are not defined in any XML standard. These tags are “invented” by the author of the XML document.

That is because the XML language has no predefined tags.

The tags used in HTML (and the structure of HTML) are predefined. HTML documents can only use tags defined in the HTML standard

XML allows the author to define his own tags and his own document structure.
XML is Not a Replacement for HTML

XML is a complement to HTML.

It is important to understand that XML is not a replacement for HTML. In most web applications, XML is used to transport data, while HTML is used to format and display the data.

My best description of XML is this:

XML is a software- and hardware-independent tool for carrying information.
XML is Everywhere

We have been participating in XML development since its creation. It has been amazing to see how quickly the XML standard has developed, and how quickly a large number of software vendors have adopted the standard.

XML is now as important for the Web as HTML was to the foundation of the Web.

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