Beginning XML, 4th Edition

When the first edition of this book was written, 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 of 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. With 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. Now 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, along with individuals, have also been using XML to distribute syndicated news stories and blog entries.

This book aims to teach you all you need to know about XML—what it is, how it works, what technologies surround it, and how it can best be used in a variety of situations, from simple data transfer to using XML in your web pages. It answers the fundamental questions:

* What is XML?

* How do you use XML?

* How does it work?

* What can you use it for, anyway?

This book is for people who know that it would be a pretty good idea to learn XML but aren't 100 percent sure why. You've heard the hype but haven't seen enough substance to figure out what XML is and what it can do. You may be using development tools that try to hide the XML behind user interfaces and scripts, but you want to know what is really happening behind the scenes. You may already be somehow involved in web development and probably even know the basics of HTML, although neither of these qualifications is absolutely necessary for this book.

What you don't need is knowledge of markup languages in general. This book assumes that you're new to the concept of markup languages, and we have structured it in a way that should make sense to the beginner and yet quickly bring you to XML expert status.

The word "Beginning" in the title refers to the style of the book, rather than the reader's experience level. There are two types of beginner for whom this book is ideal:

* Programmers who are already familiar with some web programming or data exchange techniques. Programmers in this category will already understand some of the concepts discussed here, but you will learn how you can incorporate XML technologies to enhance those solutions you currently develop.

* Those working in a programming environment but with no substantial knowledge or experience of web development or data exchange applications. In addition to learning how XML technologies can be applied to such applications, you will be introduced to some new concepts to help you understand how such systems work.

The subjects covered in this book are arranged to take you from novice to expert in as logical a manner as we could. This Fourth Edition is structured in sections based on various areas of XML expertise. Unless you are already using XML, you should start by reading the introduction to XML in Part I. From there, you can quickly jump into specific areas of expertise, or, if you prefer, you can read through the book in order. Keep in mind that there is quite a lot of overlap in XML, and that some of the sections make use of tech

David Hunter is a Senior Technical Consultant for CGI, a full-service IT and business process services partner. Providing technical leadership and guidance for solving his clients' business problems, he is a jack-of-all-trades and master of some. With a career that has included design, development, support, training, writing, and other roles, he has had extensive experience building scalable, reliable, enterprise-class applications. David loves to peek under the hood at any new technology that comes his way, and when one catches his fancy, he really gets his hands dirty. He loves nothing more than sharing these technologies with others.

Jeff Rafter is an independent consultant based in Redlands, California. His focus is one emerging technology and web standards, including XML and validation. he currently works with Baobab Health Partnership with a focus on improving world health.

Joe Fawcett (http://joe.fawcett.name) started programming in the 1970s and worked briefly in IT when leaving full-time education. he then pursued a more checkered career before returning to software development in 1994. In 2003 he was awarded the title of Microsoft Most Valuable Professional in XML for community contributions and technical expertise; he has subsequently been re-awarded every year since. Joe currently works in London and is head of software development for FTC Kaplan Ltd., a leading international provider of accountancy and business training.

Eric van der Vlist is an independent consultant and trainer. His domains of expertise include web development and XML technologies. He is the creator and main editor of XMLfr.org, the main site dedicated to XML technologies in French, the lead author of Professional Web 2.0 Programming, the author of the O'Reilly animal books XML Schema and RELAX NG and a member or the ISO DSDL (http://dsdl.org) working group focused on XML schema languages. he is based in Paris and can be reached at vdv@dyomedea.com , or meet him at one of the many conferences where he presents his projects.

Danny Ayers is a freelance developer and consultant specializing in cutting-edge web technologies. His blog (http://dannyayers.com) tends to feature material relating to the Semantic Web and/or cat photos.

Jon Duckett co-authored Wrox Press' first book on XML in 1998. After 4 years with Wrox in the UK, Jon is now a freelance web developer working with clients in the UK, US and Australia, and has co-authored 10 programming books.

Andrew Watt has been programming for 20 years, including 10 years work with the Web. He has several books in the areas of XML and XSLT to his credit and is well known for his work on XML.com.

Linda McKinnon has more than 10 years of experience as a successful trainer and network engineer, assisting both private and public enterprises in network architecture design, implementation, system administration, and RP procurement. She is a renowned mentor and has published numerous Linux study guide for Wiley Press and Gearhead Press.