This book is your guided tour to that world, so have no worries—you’vecome to the right place.The world of XML is large and is expanding inunpredictable ways every minute, but we’ll become familiar with the lay ofthe land in detail here.We also have a lot of territory to cover because XML is getting into the most amazing places, and in the most amazingways, these days. XML is a language defined by the World Wide Web Consortium (W3C, at www.w3c.org ), the body that sets the standards for the Web.This first chapter is all about getting a solid overview of that language and howyou can use it. For example, you probably already know that you can useXML to create your own elements by designing a customized markup language for your own use. In this way, XML supercedes other markup languages such as Hypertext Markup Language (HTML): In HTML, all the HTML elements you can use are predefined—and there are simply notenough of them. In fact, XML is a meta-markup language because it letsyou create your own markup language.