Okay, What Is It?

     In five words or less you mean? That can't be done. XML are initials for EXtensible Markup Language. Seems strange that the first word is "Extensible," yet they use the "X" to denote the word. My guess is that "XML" looked a lot cooler than "EXL."

DTD (Document Type Definition)

     SGML is what is known as a "meta-language;" it allows a programmer to write a DTD (Document Type Definition) that numerous pages can follow. For instance, all of you use a word processor (I would assume). You type the letter "j." Something inside of that word processor must understand what you did and display that letter. That's the DTD. You then alter the letter's size, font, and color. Again, the commands the word processor used were all understood and acted upon by using the DTD as a guide.
     HTML uses DTDs. Ever seen one of these at the very top of a page's source code:

     That's a document declaration. It states that the DTD to be used is html 3.2 in English. See that above? So, where is the DTD actually located? In the browser. Yup, Netscape, Explorer, Opera, and Mosaic are more than programs to display pretty little pictures. They are actually carrying a DTD so that when you type in a command like <B>, or <UL>, or <CENTER> the browser knows how to handle it. The browser sees the command <B>. It goes to its DTD to check what that command is supposed to do. It sees that the command makes things bold. The effect is then generated.
     The one drawback with a word processor, and HTML, is that you cannot set up your own DTDs. HTML is a very stable format of markup languages. The commands mean the same thing everywhere. The language is easy to learn because it is like playing blocks, to some extent. The tools you use never change. JavaScript is more difficult because you are actually creating the blocks before you play with them.

     Actually, that's the purpose of XML; it allows you to create your own blocks to play with.

     Okay, say you want to create a document where a certain type of text is going to be bold, italic, red, 25 point, Arial font, and a few other fancy things. And this type of text appears a great many times. In HTML you would need to write out the start and end flags every time you made the text. Or, you might say, you can set up a style sheet to do that. Well, that's the general idea here. You set up a giant style sheet-type document that acts as "mother" for all the other documents. So, what's the difference? Well, style sheets work inside of HTML documents. You have to create one to use the other. Creating your own DTD eliminates one whole step in the process -- the HTML.

So, What's Wrong With HTML?

     My personal opinion is that nothing is wrong with it. It was the first computer language that could be understood and used by the masses. It gave the Web to the common person. But those in the XML know claim HTML is clunky. They say it's become static. There's not a lot more one can do with it. Supposedly XML will allow a lot more flexibility in your Web pages. There will also be more flexibility in your HREF links. You'll be able to create cross-references and threads and other fun stuff. At least that's what the brochure says.

     The two main types of XML pages are the "standalone" and those that use a DTD. The standalone is just what it says: the page stands alone relying on the browser to have the XML DTD. In the XML language, the browser will be the XML processor. The other type of page offers the DTD to the browser so it can run the page.

The Standalone

     The standalone can be created by simply making some alterations to your current HTML document:

• Lose the current declaration statement and replace it with this one:

  <?XML version="1.0" standalone= "yes"?>< /FONT>< /FONT>

• Remember that XML IS CASE SENSITIVE. If you use caps to start the command, use caps to end the command.
• This format of caps or no caps must continue fully throughout the document. If you use IMG first, you must continue to capitalize it the rest of the way through or the XML DTD will see it as two different commands.
• All tags that do not require end tags (like <IMG> or <P>) must now be given one.
• All tags that did not require an end tag must also be given a slash before the final >

       Like so:   <IMG SRC= "pic.jpg"/></IMG>< /FONT>< /FONT>

• Each subcommand must be surrounded by quotes. (Like: TEXT="brown"</FONT>)< /FONT>
• Lose all & command and ASCII code characters.
• Make sure you are running the page in a browser that supports XML.