Markup language commonly used on the Internet, there are two, one is HTML (Hypertext Markup Language), another SGML (Standard Generalized Markup Language), and XML is a simplified version of SGML, and more scalable than SGML. The full name of the XML Extensible Markup Language, which means pages written language developed by the W3C Extensible Markup Language.XML allows designers to freely use their production web storage format, and the program between each other underground definition, transmission, and confirmation. XML programmers can use the software modules called XML processor to read the XML file, this processor not only provides access to the content and structure of the file, and can handle XML applications. Each XML file has the physical and logical structure. Physical, the file is called entity unit composed of an entity can refer to other entities and to include in the file, the file starts at the root element or document entity being. Logic, file by declaration, elements, comments, Character reference, and processing instructions consisting of all these components of the unit will be used in the file clearly labeled to represent. XML started in 1996, W3C Member in Boston held SGML meeting, developed a preliminary outline of XML. In March 1997, W3C Member first XML conference held in San Diego. In August of the same year, W3C Montana, Canada, was published XML. Specially developed XML team, this team is constantly developing new XML technology, and put forward a more comprehensive report on the W3C XML team every year to convene one or more XML meeting to promote the new features with the introduction of XML .