Beginning XML, 4th Edition

Introduction

Welcome to Beginning XML, Fourth Edition, the book I wish I'd had when I was first learning the language!

When we wrote the first edition of this book, XML was a relatively new language but already gaining ground fast and becoming more and more widely used in a vast range of applications. By the time we started the second edition, XML had already proven itself to be more than a passing fad, and was in fact being used throughout the industry for an incredibly wide range of uses. As we began the third edition, it was clear that XML was a mature technology, but more important, it became evident that the XML landscape was dividing into several areas of expertise. In this edition, we needed to categorize the increasing number of specifications surrounding XML, which either use XML or provide functionality in addition to the XML core specification.

So what is XML? It's a markup language, used to describe the structure of data in meaningful ways. Anywhere that data is input/output, stored, or transmitted from one place to another, is a potential fit for XML's capabilities. Perhaps the most well-known applications are web-related (especially with the latest developments in handheld web access—for which some of the technology is XML-based). However, there are many other non-web-based applications for which XML is useful—for example, as a replacement for (or to complement) traditional databases, or for the transfer of financial information between businesses. News organizations, ...