What is XML?

XML (eXtensible Markup Language) is a method for defining structure in documents. The philosophy behind XML is that the information (text, images, other parts) of a document can be identified through a set of rules. With these rules, a variety of software applications (like Web browsers) can interpret, display, or process data in documents.


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XML

 

The Extensible Markup Language (XML) is a subset of SGML, an enabling technology used in applications such as HTML. Its goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML. XML has been designed for ease of implementation and for interoperability with both SGML and HTML. XML is not a replacement for HTML. XML and HTML were designed with different goals:

1. XML was designed to describe data and to focus on what data is.
2. HTML was designed to display data and to focus on how data looks.

 

HTML is about displaying information, while XML is about describing information. 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 is predefined. The author of HTML documents can only use tags that are defined in the HTML standard (like <p>, <h1>, etc.). However, XML allows the author to define his own tags and his own document structure. The tags for example <to> and <from> are not defined in any XML standard. These tags are "invented" by the author of the XML document. It is important to understand that XML is not a replacement for HTML. In current and 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. XML is a cross-platform, software and hardware independent tool for transmitting information.