Like Hypertext Markup Language (HTML), Extensible Markup Language (XML) is a subset of Standardized General Markup Language (SGML) and has been designed specifically for use on the Web. XML is defined in the W3C Recommendation published by the World Wide Web Consortium. The latest version of this document is available.
XML is more complete and disciplined than HTML, and it is also a framework for creating markup languages—it allows you to define your own application-oriented markup tags.
XML provides a set of rules for structuring data. Like HTML, XML uses tags and attributes, but the tags are used to delimit pieces of data, allowing the application that receives the data to interpret the meaning of each tag. These properties make XML particularly suitable for data interchange across applications, platforms, enterprises, and the Web. The data can be structured in a hierarchy that includes nesting.
An XML document is made up of declarations, elements, comments, character references, and processing instructions, indicated in the document by explicit markup.
The simple XML document that follows contains an XML declaration followed
by the start tag of the root element, <d_dept_list>,
nested row and column elements, and finally the end tag of the root
element. The root element is the starting point for the XML processor.
<?xml version="1.0"> <d_dept_list> <d_dept_list_row> <dept_id>100</dept_id> <dept_name>R &D</dept_name> <dept_head_id>501</dept_head_id> </d_dept_list_row> ... </d_dept_list>
This section contains a brief overview of XML rules and syntax. For a good introduction to XML, see XML in 10 points. For more detailed information, see the W3C XML page, the O’Reilly page XML from the inside out, the XML Cover Pages, or one of the many books about XML.
