Extensible Markup Language (XML) is a general-purpose markup language. It is considered an extensible language because its users define their own elements. Its primary purpose is to facilitate the sharing of structured data across different information systems, particularly via local networks and the Internet.  This update to the bestselling "XML: Visual QuickStart Guide" uses concise instructions and plenty of screen shots to teach beginning users all they need to know to write XML, XSL, DTD, XML Schema, and more.  For anyone wanting to learn XML and its related technologies, this book is the most current, comprehensive, and easy-to-follow tutorial you'll find today.