XML means Extensible Markup Language. We can say that XML isn't a language but it is system for defining other languages. XML plays there role beautiful on the Internet. XML also have a life outside of the Internet, just like for people who produce documents intended to appear across multiple media and also helpful for some large-scale document publishers who have been using SGML (Standard Generalized Markup Language).

XML one of intelligence feature for the Web is how it interacts with the DOM (Document Object Model), which is an interface which defines the method for accessing data in a document. DOM, programmers can script dynamic content in a predefine way. We can say that it uses to cause a specific part of content in a browser document tree to act as in a certain way. XML will also help to resolve the problem to specifying where to display some result, and Web builders will be able to specify the structure of the document. There are some XML-based languages is already in use--Microsoft's Channel Definition Format (CDF) and more are on the way, including the Resource Definition Format (RDF) and the Open Software Description (OSD).

XML also become a standardized method for the exchange of data as well as documents. So XML become a way for databases from different vendors to exchange of data across the Internet. XML will also be used in a different ways. Firstly it is used for data interchange between users and machines, just like Web server to a user's browser.

The other thing is used for data exchange between applications, or from machine to machine. There are mostly two types of XML documents: well-formed and valid. A well-formed XML document follows the general rules of XML syntax, which are we can say that are either of HTML or SGML. And another type is Valid XML documents are documents that prepare for a specific Document Type Definition (DTD).

Confirming the validity of XML documents is largely the work for XML-capable browsers need only check for well-formed in order to read XML documents.

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