Ivor Horton's Beginning Java™ 2, JDK™ 5th Edition

22.1. XML

XML, or the Extensible Markup Language to give it its full title, is a system- and hardware-independent language for defining data and its structure within an XML document. An XML document is a Unicode text file that contains data together with markup that defines the structure of the data. Because an XML document is a text file, you can create XML using any plaintext editor, although an editor designed for creating and editing XML will obviously make things easier. The precise definition of XML is in the hands of the World Wide Web Consortium (W3C), and if you want to consult the current XML specifications, you can find them at http://www.w3.org/XML.

The term markup derives from a time when the paper draft of a document to be printed was marked up by hand to indicate to the typesetter how the printed form of the document should look. Indeed the ancestry of XML can be traced back to a system that was originally developed by IBM in the 1960s to automate and standardize markup for system reference manuals for IBM hardware and software products. XML markup looks similar to HTML in that it consists of tags and attributes added to the text in a file. However, the superficial appearance is where the similarity between XML and HTML ends. XML and HTML are profoundly different in purpose and capability.

Firstly, although an XML document can be created, read, and understood by a person, XML is primarily for communicating data from one computer to another. XML documents will therefore ...