Foreword

XML—the Extensible Markup Language—is an approved Recommendation of the World Wide Web Consortium (W3C).

That is a very important statement, as we'll see in a minute.

If you're looking at this book, you are aware that XML is rapidly becoming the base of a Brave New Web of smart data and electronic commerce. Thousands of people are building it into Web sites, products, and industry standards.

And beyond the Web, enterprise software companies like SAP, BAAN, IBM, and Oracle are supporting XML for object repositories, data interchange, and development tools. In short, XML is emerging as the universal format for information exchange.

There are many solid technical reasons for this extraordinary acceptance:

• Powerful expressive capability for data and documents

• Efficient implementations, tuned for networked environments

• Proven track records of XML's parent, SGML, and its sibling, HTML

But that very first statement is perhaps even more important. Even arch competitors like Microsoft, Sun, IBM, and Netscape—who disagree on most things—agree on XML. And they, and the hundreds of other members of the W3C, have documented that agreement in the form of the official text of the XML Recommendation.

That document is the One True Source of information about the XML language. By design, it is expressed in rigorous, elegant (in the mathematical sense, which is to say, "efficient"), formal, and concise language. Parts of it are intended to be read by computers; the rest is intended to be read by people who are comfortable reading things that are intended to be read by computers.

For earth people—even for most programmers—it's a daunting read, indeed!

Which is a shame, because if you really want to understand every detail of a language, you should read the original spec. The authors in my Definitive XML Series have read the XML spec, and we've done our best to make our books accurate and consistent with it. But for the ultimate reference on the details, only the spec itself will do.

And now, thanks to Bob DuCharme and this book, the XML spec has become much more accessible. Bob is a full-time practicing SGML/XML expert, author, and frequent speaker at industry conferences.

In preparing XML: The Annotated Specification, he studied all of the three million bytes of email and scores of supporting documents that were generated during the long development effort for XML. From it, he has created illuminating commentary on every part of the W3C Recommendation, plus more than 170 new usage examples.

With the permission of the W3C, the entire Recommendation is presented verbatim in this book. Intermingled with it—but typographically distinct—are Bob's explanations, hints, insights, and examples. Together they form a marvelous reference to what is fast becoming the Web's most important content standard.

Whatever your interest in XML, as user or implementor, you'll want XML: The Annotated Specification.

Charles F. Goldfarb

Saratoga, CA

November, 1998