XML, or EXtensible Markup Language, is a platform-independent way to represent data. Simply put, XML enables you to create data that can read by any application on any platform. It is based on the same tag-based technology that underlies HTML.
For example, suppose you want to use XML to store information about a transaction. This transaction originates on a salesman’s iBook, so it will be stored there. But it will then be sent to the data application on the individual’s server, and ultimately archived on a mainframe, so it needs to be very flexible.
XML is fairly straightforward to use, once its structure is understood. It also provides several different methods by which you can control the structure, and even the content, of data. The flexibility of XML means that it’s useful for so many applications, such as configuration files, Web services, data storage, and so on. Since its introduction, developers have found numerous uses for XML.
The most obvious use of XML is to store data. XML provides advantages for both data-centric information (such as the data you find in a database) and document-centric information (such as data you store in XML so you can display it differently in different environments.)