It's easy to get lost when talking about XML. It has grown into a huge topic, inspiring so many technologies and branching into new areas. Anywhere there is information, you'll find XML, or at least hear it scratching at the door. So priority number one is to get a broad view, ask the big questions, so that you can find your way through the dense jungle of standards and concepts.

There are a few questions that come to mind. What is XML? We will attack this from different angles. It's more than the next generation of HTML. It's a general-purpose information storage system. It's a markup language toolkit. It's an open standard. It's a collection of standards. It's a lot of things, as you'll see.

Where did it come from? It's good to have a historical perspective. You'll see how XML evolved out of preceding efforts like SGML, HTML, and the earliest presentational markup.

What can I do with XML? A practical question, again with several answers: store and retrieve data, ensure document integrity, format documents, and support many cultural localizations. And the following section answers the other question, what can't I do with XML? You need to know about the limitations, in case it isn't a good fit with your problem.

How do I get started? Without any hesitation, I hope. I'll describe the tools you need to get going with XML and test the examples in this book. From authoring, validating, checking well-formedness, transforming, formatting, and writing programs, you'll have a lot to play with.

So now, let us dive into the big questions. At the end, you should know enough to decide where to go from here. Future chapters will describe topics in more detail, such as core markup, quality control, style and presentation, programming interfaces, and internationalization.

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