Presenting XML

ISBN: 1-57521-334-6

Authors:

• Richard Light, Lead Author. Richard Light is a freelance consultant and software developer specializing in museum information systems. He has tracked SGML since the late 1980's and published his "SGML Tagger" software in 1993. He is currently the treasurer of the International SGML Users Group.
• Simon North, Contributing Author. Simon North is an experienced technical writer who has been involved with SGML since 1989 He was a participant in the Dutch CALS/SGML standards activities. Simon wrote Chapters 16, 17, and 18 and Appendices A and B.
• Charles Allen, Contributing Author. Charles Allen is the cofounder of WebMethods. He was also a founding member of Open Environment Corporation. Charles wrote Chapter 15 of Presenting XML.

Pages: 391

Intended Audience:

Presenting XML was the first book on XML to hit the market. First available at Seybold San Francisco 1997, Presenting XML was designed to introduce XML as the " new technology, now". The book was designed to address a range of levels of interest in this new language for the Web. The book addresses the broad strategic overview of XML technology and its potential impact on the World Wide Web. It also attempts to present the technical detail of XML as well.

It is important to note that this is a very early title on XML. Today, some of the content is already dated. But the author notes that at the time this book was authored "the XML specification is very much a moving target."

Summary:

Presenting XML is divided into 4 parts and has two appendices.

Part I is "Introducing XML." This part gives an overview and history of XML. It begins by explaining the concept of generalized markup. According to the authors, generalized markup is markup which indicates the structural significance of text within the document as a whole. XML is therefore an example of generalized markup, while RTF is not. The authors go on to provide a high level explanation of SGML and go on to explain how HTML is really an application of SGML for the Web. Limitations of HTML are then introduced and XML is proposed as the solution to the shortcomings inherent in HTML. Although a chapter is dedicated to explaining how to implement XML and the XML tool set, this is an early text and does not contain good coverage of this topic.

Part II of the book examines "XML in Detail." It begins by explaining the XML approach and how XML interoperates with both HTML and SGML. The design goals of this new standard are reviewed. Emphasis on the simplicity and ease of use is clear. Having said that, detailed technical discussions of the details of XML (such as primitive constructs, white space handling, and logical and physical structure) are presented. Logical structures include the concepts of "well-formedness," elements, attributes, content models, cross references, and groves. Finally an "XML Rules Book" is presented. It reviews the rules particular to XML, including EMPTY and ANY element declarations, handling mixed content, and the XML Declaration.

Part III focuses on "Using XML." The author begins by discussing how to make the transition from existing HTML files to XML files. A typical HTML Web page is converted into XML. Along the way the concept of "well-formedness" is made real as the "tag soup" of the Web page is transformed into an orderly XML document. This is a particularly good way for a beginner to begin to understand the differences between HTML and XML.

Once the reader understands how XML can provide structure, the next step, the addition of content is explored. At this point the concept of an XML DTD is introduced and simple content is added to the document. Beginning with the topic of DTDs, this part becomes much more technical and more difficult for the reader. Finally the concepts behind XML linking are introduced and a concrete example of an XML style sheet is presented. Although these concepts are presented in a simple and straightforward way, the novice may still be left feeling they are a bit over their technical depth.

The last chapter of Part III is titled "Automating the Web." Charles Allen writes this part of the book. It explores the use of XML to provide practical, low-cost means for business systems to integrate over corporate Intranets and the Web. According to Allen, XML will change the Web from an "access medium" to an "integration platform" for applications that can share and process data. Today the only technologies we can count on in the near term are HTTP, HTML, and SSL. XML adds the capability of specifying metadata to define functional services over these protocols to enable developers to have a common ground. The concepts of channels and agents and the role of Channel Definition Format (CDF) are introduced and XML is positioned as being poised to "transform the Web."

Part IV of "Presenting XML" focuses on the future. This book was released in September 1997 when XML was still a Draft and XSL (eXtensible Style Language) had not yet been introduced. The author discusses the early XML software, describes the ongoing standards process, and discusses potential applications for XML.

Two appendices are provided. The first discusses the differences between XML and SGML. This is clearly written for the SGML audience and should prove helpful in making SGML data XML compliant as well as making SGML DTDs XML compliant. The second appendix provides a bibliography for those who want to learn more from related publications.

"Presenting XML" is a good first publication on XML. It provides fundamentals of XML from several points of view including the HTML view, the Systems/Web Master view, and the SGML view. It gives readers practical examples of how a transition to XML can be made and provides some insights into the development that XML will see in the upcoming year. If you want to learn more about the new technology of XML, this is a good title to add to your professional library. You can order it from GCA or pick it up at the XML conference in Seattle this March.