Introduction to XML
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XML was designed to transport and store data.
HTML was designed to display data.
What You Should Already Know
Before you continue you should have a basic understanding of the following:
If you want to study these subjects first, find the tutorials on our Home page.
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 ...view middle of the document...
It has sender and receiver information, it also has a heading and a message body.
But still, this XML document does not DO anything. It is just pure information wrapped in tags. Someone must write a piece of software to send, receive or display it.
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 (like , , etc.).
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 a W3C Recommendation
XML became a W3C Recommendation 10. February 1998.
To read more about the XML activities at W3C, please read our W3C Tutorial.
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 has adopted the standard.
XML is now as important for the Web as HTML was to the foundation of the Web.
XML is everywhere. It is the most common tool for data transmissions between all sorts of applications, and is becoming more and more popular in the area of storing and describing information.
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XML Separates Data from HTML
If you need to display dynamic data in your HTML document, it will take a lot of work to edit the HTML each time the data changes.
With XML, data can be stored in separate XML files. This way you can concentrate on using HTML for layout and display, and be sure that changes in the underlying data will not require any changes to the HTML.
You will learn more about this in a later chapter of this tutorial.
XML Simplifies Data Sharing
In the real world, computer systems and databases contain data in incompatible formats.
XML data is stored in plain text format. This provides a software- and hardware-independent way of storing...