Extreme Markup
By Michael Floyd
In the good ol' days, there were frames, tables, IMG tags, and anchors. HTML was, and is, great at marking up documents for publishing. And after all, HTML is the language of the Web. So why is there all this interest in the eXtensible Markup Language (XML), and where did it come from?
The short answer to the second question is the Standard Generalized Markup Language (SGML). SGML is not a markup language, per se. Rather, it's a metalanguage that lets you create your own customized markup language. This is, in fact, what HTML is: an instance of specific tags defined in SGML. More accurately, HTML can be fully specified by a particular Document Type Definition (DTD) in SGML. So, at the next party when you hear that SGML is the grandfather of HTML, you can respond that HTML is actually the most widely deployed SGML application in the world.
The answer to the first question is that HTML's original draw -- its simplicity -- is now its greatest drawback. Users want HTML to do things it was never designed to do, and as a result the HTML 4 specification has added new complexities to a once elegantly simple language. The bigger problem is that we'll have to wait for the next generation of browsers to fully support the new specification. And if we, as developers, choose to use these new features, we risk excluding older, noncompliant browsers.
Recognizing these and other problems, the W3C went back to the SGML drawing board and decided that if HTML represents the proverbial fish, then SGML is the pole.
