XML Introduction

XML is designed to transmit and store data.

HTML is designed to display data.

XML stands for eXtensible Markup Language.

Extensible Markup Language (XML) is a markup language that was simplified and modified from the Standard Generalized Markup Language (SGML). Its main applications include Extensible Markup Language, Extensible Stylesheet Language (XSL), XBRL, and XPath, etc.

Prerequisites

Before you continue learning, you need a basic understanding of the following:

  • HTML
  • JavaScript

If you wish to learn these items first, please visit these tutorials on ourhomepageto access these tutorials.

What is XML?

  • XML stands for EXtensible Markup Language.
  • XML is a markup language very similar to HTML.
  • XML is designed to transmit data, not display data.
  • XML tags are not predefined. You need to define your own tags.
  • XML is designed to be self-descriptive.
  • XML is a W3C Recommendation.

Differences Between XML and HTML

XML is not a replacement for HTML.

XML and HTML are designed for different purposes:

  • XML is designed to transmit and store data, with its focus on the content of the data.
  • HTML is designed to display data, with its focus on the appearance of the data.

HTML is designed to display information, while XML is designed to transmit information.

XML Does Nothing

Perhaps this is a bit hard to understand, but XML does nothing. XML is designed to structure, store, and transmit information.

The following example is a note from Jani to Tove, stored as XML:

<note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>

The note above is self-descriptive. It contains information about the sender and recipient, as well as a title and a message body.

However, this XML document still doesn't do anything. It is just pure information wrapped in XML tags. We need to write software or a program to transmit, receive, and display this document.

With XML, You Can Invent Your Own Tags

The tags in the example above are not defined in any XML standard (such as <to> and <from>). These tags are invented by the creator of the XML document.

This is because the XML language has no predefined tags.

The tags used in HTML are all predefined. HTML documents can only use tags defined in the HTML standard (such as <p>, <h1>, etc.).

XML allows creators to define their own tags and their own document structure.

XML is Not a Replacement for HTML

XML is a complement to HTML.

XML will not replace HTML; it's important to understand this. In most web applications, XML is used to transmit data, while HTML is used to format and display data.

The best description of XML is:

XML is an information transmission tool independent of software and hardware.

XML is a W3C Recommendation

XML became a W3C Recommendation on February 10, 1998.

To learn more about W3C XML activities, please visit ourW3C Tutorial。

XML is Everywhere

Currently, XML plays a role on the Web no less important than HTML, which has always been the foundation of the Web.

XML is the most commonly used tool for data transmission between various applications.


Other Extensions