This is not a general XML book; it is a book on one specific application of XML. What you'll find here is as much XML and XSLT as is necessary for a sequence of very practical tasks :
structuring your web site content into cleanly separated semantic layers ;
developing a custom XML markup vocabulary for each layer;
automatically validating both markup and structure of content;
transforming content from source XML to browser-ready HTML using XSLT ( optionally with generation of images and other non-HTML objects); and
integrating the content markup and transformation system with existing web development frameworks and other software.
Building the backbone. The point of using XML in web design is to separate content from presentation ; the above items cover the complete transition from the former to the latter. Simply put, we focus on developing the best source markup for your content and programming the most efficient transformation into your chosen presentation style.
An XML web site may include other components , such as a database, a dynamic engine, or a maintenance back-end. There is a wide range of auxiliary tools and architectures compatible with an XML-based web site. Many of them are mentioned in this book, and a few are explored in detail (notably Cocoon, Chapter 7). However, the content-to-presentation assembly line is the backbone of any XML web site and our main focus of attention in this book.
Usability and portability. In a web development context, the term usability normally refers to how easy to use a web site is for a visitor. In this book, however, I would like to redefine this term by focusing on a different aspect of usability that is too often ignoredusability of a web site for its developers, authors, editors, and maintainers. With the Web growing more and more collaborative, this aspect is becoming critical.
Using semantic XML for content markup is already a big step toward liberating web authors from worrying about things they don't need to worry about. But semantic XML is only an idea; how you implement this idea will seriously affect the "authorability" and "maintainability" of your site. This is where this book, with its pervasive ideas of simplification, abbreviation, and readability, might be useful.
Another important theme of the book is portability . Again, this term usually describes a web site's viewability and functionality across browsers and platforms. It's not less important, however, that before a web site gets to your browser, it must be developed and authored often in different environments and on different platforms. We touch on this server-side aspect of portability with regard to the XML/XSLT workflow.