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What is XML?

XML, a text-based markup language developed by the W3C used to describe the structure of data. XML, a metalanguage, used to describe other languages is becoming a fast standard for information interchange on the web. XML is a subset of the Standardized Generalized Markup Language (SGML). Unlike HTML, the tags in XML are not predefined, rather user can create custom, self-descriptive tags related to that context. XML allows data to be displayed in different ways according to the tags specified.

Importance of XML

  • XML is free and tags are unlimited.
  • XML file can be created using a simple text editor; No separate software is required.
  • With XML, any complex data structures like news feeds, invoices etc., can be defined in a easy manner.
  • XML do not specify the way to display the data instead tells the type of data.
  • XML is style-free, which provides flexibility in producing output in some new format like html, pdf etc.
  • XML is a emerging standard for information interchange between different computer systems.

Parts of a XML file

XML file consists of four parts namely, XML Document(Content), XML Document Type Definition(DTD), XML Parser(Conformity Checker) and XML Application. XML document in turn consists of five Classes; Elements, Entities, Comments, Processing Instructions and CData Definitions.

XML File - Example

<?xml version="1.0"?>
    <student type="regular">
    <student type="lateral">

XML File Example - Explanation

  • <?xml version="1.0"?> - refers to Processing Instructions.
  • Each student as a whole refers to the document.
  • Student is a parent element; Name, Id, Child are child elements of student element Student.
  • Type is an attribute.
  • XML parser is one which reads and validates a XML document.
  • Text placed inside a XML parser will be ignored by a parser. Syntax of CDATA section is included between "<![CDATA[" and "]]>".