Extending Your Markup: An XML Tutorial

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XML introduces a family of languages to provide a more semantic management of information than HTML. By now, no doubt, you’ve heard the acronym XML. You’ve probably also heard that XML (a) is simple and (b) will solve all your problems. Sounds like magic, doesn’t it? But then you look a little deeper and encounter more three-letter acronyms, like DTD, XSL, RDF, and DOM. You begin to doubt XML’s simplicity (and you never believed XML could solve all your problems in the first place). In this short tutorial I present what I think are the essential concepts of XML, and hopefully will convince you that despite the hype, XML is important for presentation, exchange, and management of information. More Meaningful Markup The Standard Generalized Markup Language (SGML) is a rather complicated language that lets you define structure for documents. The Hypertext Markup Language is an application of SGML that has a fixed set of markups. HTML is primarily used for layout on the Web. It tells nothing about the content of the data. Both SGML and HTML heavily influenced the development of the Extensible Markup Language (XML), a semantic language that lets you meaningfully annotate text. Meaningful annotation is, in essence, what XML is all about. Figure 1a shows a bibliography entry in HTML; Figure 1b shows that same entry written in XML. Because the structure of the information in Figure 1b is more explicit, it is much easier for humans to read and computers to process.

Extending Your Markup: An XML Tutorial