What is XML

XML is a text-based markup language that is fast becoming the standard for data interchange on the Web. As with HTML, you identify data using tags (identifiers enclosed in angle brackets, like this: <...>). Collectively, the tags are known as "markup".

But unlike HTML, XML tags tell you what the data means, rather than how to display it. Where an HTML tag says something like "display this data in bold font" (<b>...</b>), an XML tag acts like a field name in your program. It puts a label on a piece of data that identifies it (for example: <topic>...</topic>).

XML is an open, text-based markup language that provides structural and semantic information to data. This "data about data," or metadata, provides additional meaning and context to the application using the data and allows for a new level of management and manipulation of Web-based information. XML, a subset of the popular Standard Generalized Markup Language (SGML), has been optimized for the Web. This helps make XML a powerful, standards-based complement to HTML that could be as important to the future of information delivery on the Web as HTML was to its beginning.

XML is intended to be used by content creators as well as by programmers. Since XML is text-based, it can be read and worked with easily in relatively nontechnical situations, but its ability to organize, describe, and structure data also makes it ideal for use in highly technical applications. XML thus provides common ground for creating structured data and making it available for manipulation and display.