XML - An Introduction

Today, we're deeply ensnared in the World Wide Web. Forests of techspeak, along with metaphors like "information superhighway", "global village" and "Infobahn" litter our conversations. Offline, you're off-life, standing still as the information age hurtles past. And so the moral of the day is "Get online: there's gold in those nets. You never know what you might catch!"

This pounding rain of hype has been a good incentive. From a few academics and hardcore hobbyists, Internet growth has gone nuclear. 300 million have moved online; 55 million use the Web regularly. And HTML - HyperText Markup Language - is responsible. HTML spins ordinary data into a World Wide Web, touching anyone, anywhere, anytime. So now, the global reach that was once accessible only through expensive media channels, is available to the masses.

Today's HTML has advanced far beyond its first humble steps. But its virtues now shackle it; HTML can no longer move forward. So its makers have created a new language: XML.

What is XML? To answer this, we must know:

• Why HTML worked
• Why HTML no longer works
• Why XML will pick up where HTML left off

Why HTML Worked

HTML outlines hypertext structure. Ideally, hypertext is data that follows a path imposed by user whim, linked and experienced independent of where it, and its user, are located. Though the Web hasn't reached this ideal, and perhaps never will, HTML's design grasps for it, addressing three key concerns in data delivery:

1. Linking: Data is linked in HTML - one piece carries you to another.

2. Simplicity: HTML is simple and easy to learn.

3. Portability: HTML is stripped down, so it's portable - especially over networks.

Each of these elements, when hard-wired into data by commands called markup, make hypertext. Markup says this is a paragraph <P>, this is a picture <IMG SRC="picture.gif">, and this is a link <A HREF="link.html">Link</A>.

For example, take a line like:

Dick likes Jane. Run, Jane, run.

Then add markup:

<A HREF="dick.html">Dick</A> likes <A HREF="jane.html">Jane</A>. <A HREF="run_jane.html">Run, Jane, run.</A>

And you get:

Dick likes Jane. Run, Jane, run.
[Note: these particular links don't actually go anywhere]

Anyone interested in Dick and Jane can then follow a link to more information on Dick, or Jane, or on where Jane might run.

HTML was the first means of targeted data transfer to so many people so easily. Radio and TV unleashed a lot of data, but the flood was indiscriminate. Computers allowed greater user interaction, but were limited by their location and multi-platform inconsistencies. Only HTML allowed data to transcend the twin tyrannies of distance and incompatibility.

But then, the cracks began to show…