This month, I’m moving away from my standard review format to address some recent changes in the mark-up languages now available on the Web. I’m talking in particular about two recent W3C specs for markup languages:
The introduction of HTML 4.0 and the creation of a group to define XML (extensible Markup Language). They promise more flexibility, but also more headaches for developers attempting to offer the same experience to both Internet Explorer and Netscape Communicator users.
Let’s start by looking at HTML 4.0.
Among the most interesting trends presented by HTML 4.0 is the push to move more functionality away from the server and toward the client. As a result, HTML documents will soon be able to display types that are similar to database searches. Combined with the general trend toward push, this means that you will soon be able to perform semi-complex searches in Web forms without even being connected to the Net.
Also close to the object orientation of the new HTML is the full support of stylesheets. While this may not seem like much, considering that both Communicator and Internet Explorer support them, the clear delineation of where the W3C stands when it comes to style sheets will be a tremenduous help in the future if it generates a consensus between Netscape and Microsoft on implementation.
A few other elements, such as movements in forms and frames, allow developers to create more compelling content. On the forms side, you can now provide keyboard shortcuts for controls. Frames are finally seeing the arrival of in-line frames (the IFRAME tag was introduced by Microsoft in IE 3.0 but never formally endorsed and never supported by Netscape), which will allow Web designers to create compound documents by placing frames directly into HTML documents. As such, one could put a frame inside a Web page, keeping other things around it. This has great applications if you want to have a slide show embedded in a page, for example.
Of course, this does not address all the challenges Web designers come up with. Enter XML, the extensible Markup Language, a metalanguage to let you design your own markup language. Yes, You read it properly, XML lets you define your own customized markup languages for many classes of document. It can do this because it’s done in SGML, the international standard metalanguage.
To understand how the W3C came up with XML, you’ve got to look at the eolution of HTML. As time goes on, HTML is getting more and more crowded and fails to support certain tags. The reason some tags are not supported is that they may be considered too specific to a particular industry. An ISBN number, for example, is often used in the book industry (ISBN numbers are used by libraries and bookstores to identify books) but totally useless outside of it.
As a result, XML was born, giving Web developers a chance to create their own markup language.
The basic foundation for a XML document is a file, called a Definition Table Document (or DTD), defining the tags you create. A tag is defined in two parts: what it does and what it looks like. As a result, XML can be used in a variety of ways. CDF, Microsoft’s push solution, is an example of an XML languagage. But more important is the fact that XML Dtds will probably be created for vertical industries. As a result, XML will probably be very helpful in EDI (Electronic Data Interexchange), allowing companies using it to move to an Internet transport format instead of using proprietary networks to move their data.
If you want more information those two new markup languages, you might want to check out the World Wide Web Consortium web site at http://wwww3.org.