Learning XML
What's up with XML? Is it a revolutionary technology destined to be our livelihood the next few years, or a passing fad? Is it a universal standard specified by the W3C? And for some, the most nagging question is "how the heck do I learn it?".
XML derives its power from the fact that it can represent anything the human mind can conceive. And that representation is very readable both for a human and for a machine. The concept is so clean that upon understanding it, my first question was "why didn't I invent XML?". I certainly have the intelligence to have invented it -- XML's not rocket science. I've needed it for years, but had to "roll my own" every time I needed a configuration file or data format. So get familiar with XML. Whether you're in the Microsoft world or the Open Source world, or somewhere in between, you'll need to interface with it in the next couple years.
What is XML?
One possible answer is that XML is a markup language. Another possible answer is that XML is a styles-based markup language, rather than an appearance-based markup language like HTML.
I think a much better definition for XML is a specification for a markup language that can be used to represent almost any concept.