The combination of hypertext and a global Internet started a revolution. The Extensible Markup Language (XML) is a new language designed to make information self-describing. This simple-sounding change in how computers communicate has the potential to extend the Internet beyond information delivery to many other kinds of human activity. Since XML was completed in early 1998 by the World Wide Web Consortium, the standard has spread like wildfire through science and into industries ranging from manufacturing to medicine.