Day One: What Is XHTML?
XHTML expert Molly Holzschlag walks you through the basics of XHTML, shows how it compares to HTML, and tells what it means for the world of Web development.
XHTML is the Extensible Hypertext Markup Language. Technically speaking, it is a reformulation of HTML into an XML application. But what does this mean in simple terms?
Let's begin with the language most familiar to the majority of people: HTML. HTML has been around for a long time now—close to 10 years. Of course, most people have been using it for around six years or less. Originally a method of marking up simple Web documents—adding headers, paragraphs, and links—HTML turned into a language of design, via rapid growth and demand. It was never intended for this, though. Rules were broken or rewritten, arbitrarily made up to accommodate the hunger for this fascinating medium known as the Web.
By the time the last available HTML standard, HTML 4.01, was set forth, many attempts had been made to reign in this unruliness and to offer people more professional ways of authoring and designing their documents. But the HTML 4.0 standard itself is still poorly understood, largely because HTML is fairly easy to learn, poor habits prevail, non-standards compliant software exists, and, perhaps most interestingly, browsers forgive. HTML 4.0 tried desperately to make a statement that people should follow a standard and that browser developers should support that standard. But again, the message seems to never have been clearly expressed.
In addition, the problems with HTML in general ran very deep. This messy state of affairs was really becoming bad enough to warrant a re-examination of the language itself.
Like HTML, XML, the Extensible Markup Language, was structured from SGML, the Standard Generalized Markup Language. It's important to point out that SGML is a metalanguage—or, in simplistic terms, it is a language for creating languages. Although HTML is a markup language itself, XML, like its SGML parent, is a metalanguage, too. It describes rules for creating markup languages, and these rules are especially suitable and streamlined for the Web.
So, HTML was re-examined in the context of XML, and XHTML 1.0 was born. XHTML is considered to be an application of XML. In other words, it applies the rules inherent to XML, and it does so using the already familiar vocabulary of HTML.
An author, instructor, and designer, Molly E. Holzschlag brings her irrepressible enthusiasm to books, classrooms, and Web sites. Honored as one of the Top 25 Most Influential Women on the Web, Molly has worked in the online world for an almost unprecedented decade. She has written and contributed to more than 10 books about the Internet and, in particular, the Web.
Molly holds a B.A. in communications and writing and an M.A. in media studies from the New School for Social Research. You can visit her Web site at http://www.molly.com/.
Molly's most recent publications are Special Edition Using XHTML(Que, November 2000), Sams Teach Yourself Adobe LiveMotion in 24 Hours (Sams, June 2000), and Special Edition Using HTML 4.0, Sixth Edition (Que, December 1999).