If you're a developer looking for a quick and useful reference on some of the fundamental standards around XML, look no more. In a handy paperback edition priced at $24.99, Essential XML Quick Reference from Addison-Wesley is a great buy. Regardless of which programming language you use, this book stands out as a great reference on the basic constructs of XML and its usage.

Organization
The book is organized into 10 chapters and contains a detailed index, which is actually quite useful given the new terms that XML and its associated standards have introduced. Each of the 10 chapters focuses on one essential aspect of XML - XML 1.0 and Namespaces, DTD, XPath, XPointer (with XInclude and XML Base), XSLT, SAX, DOM, XML Schema (covered in two chapters), and SOAP. Even though the book is really a technical reference, each chapter provides a basic introduction to its topic. I think that in the next edition of the book the authors may want to extend the topic introductions by a paragraph or two. Even though a reference book isn't really expected to teach the technology, readers would definitely benefit from an extended introduction. This is particularly appropriate for complex chapters such as the ones on SOAP and XML Schema.

My favorite is the chapter on XPath, which provides a handy reference to the expressions and the core function library. I also liked the related chapter on XSL Transformations (XSLT). The two long, detailed chapters on XML Schemas, which compose more than 30% of the book, are quite useful as well. This comprehensive coverage is quite appropriate, given that the XML Schema specification is probably one of the most complex and detailed in the set of core standards around XML. A chapter on XSL-FO would be a nice addition to the next edition to cover use of XML in print media.

Where Is myML?
As is probably clear by now, the book is all about the "core" standards around XML. What it's not about is the ever-expanding list of MLs in your favorite industry, application, etc. So if you're looking to get a perspective on the various markup languages that have been developed around human resources, manufacturing, financial services, and so on, you'll have to look elsewhere.

Code Snippets
In most places, the authors have done a good job of keeping the code snippets short and sweet to convey the message. In scenarios in which a detailed code example is required, particularly in the chapters on DOM and SAX, the authors have chosen to rely on Java and Visual Basic as the two programming languages to demonstrate the code. Being a hands-on technologist, I do like code examples, but I have to agree with the authors' style of short snippets. However, to satisfy all the C#, Perl, C++ developers, it might be a good idea to have the source code in different programming languages on a Web site. In all, I think the authors' decision to focus more on the underlying XML semantics than programming constructs is a good decision that maintains the focus of the book.

What About Web Services?
Web services, as we all know, is probably one of the most popular and growing areas in which XML is being used. Though the book doesn't focus on Web services, it does include a dedicated chapter on SOAP 1.1. My suggestion for the authors and publishers is to add a chapter on the related WSDL (Web Services Description Language) as well, which would provide a more thorough introduction to Web services. Also, I would encourage the authors and publishers to team up again and work on an Essential Web Services Quick Reference.

Online Version
An online version of the book (nonprintable but searchable PDF files) is available. Although I love to read books in print, the online edition is a great companion when I'm on the road.

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Essential XML Quick Reference
A Programmer's Reference to XML, XPath, XSLT, XML Schema, SOAP, and More by Aaron Skonnard and Martin Gudgin

Published by: Addison-Wesley
Pages: 402
ISBN: 0201740958
List Price: $24.99