The magazine of the Melbourne PC User Group SGML/XML/XHTML Resources - Part 5 Major Keary majkeary@netspace.com.au

When XHTML was released the available documentation suggested the intention of W3C was to provide a transitional markup language that would lead users to XML. Some commentators were describing XHTML as a "bridge" to XML. 

Since then the position has become more clear. XHTML is an XML application intended to be the "foundation language for the future of the Web" [HTML & XHTML - The Definitive Guide]. The strength of XML is not so much its direct application to document creation, but that it enables development of new, specialist markup languages: "XML enables communities of users to create languages that best capture their unique data and ideas. Mathematicians, chemists, musicians, and professionals from hundreds of other disciplines can create special tags that represent unique concepts in a standardized way". 

XHTML is a prime example of a markup language created for a particular purpose; there are, of course, special considerations: it must be readable by existing browsers, and new browsers must recognise HTML tags for a transition period. Thus, HTML will co-exist with XHTML for some time, but future browsers will provide diminishing support for some current HTML features . 

A number of tags have been deprecated, which means they are to be phased out. They are mainly those that perform presentation functions - such as Strike-out, underline, and font control - that will be handled by style sheets. 

Just released is the fourth edition of HTML & XHTML - The Definitive Guide, which brings O'Reilly's long standing HTML guide up to date with current developments in the transition to XHTML.

The book has been written "for anyone interested in learning the language of the Web, from the most casual to the full-time design professional". If you are a computer newbie, or have had no experience of using markup languages, I suggest you begin with one of the elementary texts; if you have a real interest in using HTML/XHTML it won't take long to be ready for The Definitive Reference. 

This book has a number of features that impress me. It does cater for users from casual to professional. The authors provide useful background and other explanatory material that puts XHTML into a big picture context. It addresses the problem of browser variations; the same HTML document may display differently on different browsers, but the book describes ways of at least minimising potential problems. It progresses from simple HTML through the use of style sheets, JavaScript, forms, and tables. The information is presented in clear English and supported by useful examples. Last, but by no means least, the authors do not set out to stampede users into XHTML; if you are comfortable with HTML, just keep on using it - just keep in mind that deprecated tags are best avoided. For those who want to move into XHTML it is an excellent guide.

Cascading Style Sheets and JavaScript are subjects in their own right, but the treatment here is probably sufficient for most users. It certainly enable users to orient themselves in what may seem to be a confusing landscape. 

Other chapters cover Rules, Images, and Multimedia; Links and Webs; Formatted Lists; Forms; Tables; Frames; Executable Content (applets, objects, JavaScript, and embedded content); Dynamic Documents (push and pull); and Netscape Layout Extensions.

There are also detailed discussions of XML and XHTML, and a chapter devoted to Tips, Tricks, and Hacks.

Appendices include an HTML grammar; HTML/XHTML tag quick reference; CSS properties quick reference; the HTML 4.01 DTD; the XHTML 1.0 DTD; a list of character entities; and a list of colour names and values. A tear-out quick reference card should be of great use to regular users.

The book is not just a list of tags and the like, but provides in-depth explanations of concepts and processes. In particular, for those who want to understand the Document Type Definition the listings (appendices D and E) and discussion in the text should provide a good grounding. 

A useful feature is the boxed information for each tag; these lay out in tabular form the function, attributes, contents, and use. 

Reprinted from the November 2000 issue of PC Update, the magazine of Melbourne PC User Group, Australia

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