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Introduction to XML For Web Developers
History of XML  

XML emerged as a way to overcome the shortcomings of its two predecessors, SGML and HTML which were both very successful markup languages, but which were both flawed in certain ways.

SGML, the international standard for marking up data, has been used since the 80s. SGML is an extremely powerful and extensible tool for semantic markup which is particularly useful for cataloging and indexing data. Like XML, SGML can be used to create an infinite number of markup languages and has a host of other resources as well.

However, SGML is pretty darn complex, especially for the everyday uses of the web. Not only that, but SGML is pretty expensive. Adding SGML capability to a word processor could double or triple the price. Finally, the commercial browsers made it pretty clear that they did not intend to ever support SGML.

HTML on the other hand was free, simple and widely supported. HTML was originally designed at CERN around 1990 to provide a very simple version of SGML which could be used by "regular" people. As everyone knows, HTML spread like wildfire.

Unfortunately, HTML had serious defects that we discussed earlier.

So in 1996, discussions began which focused on how to define a markup language with the power and extensibility of SGML but with the simplicity of HTML. The World Wide Web Consortium (W3C) decided to sponsor a group of SGML gurus including Jon Bosak from Sun.

Essentially, Bosak and his team did to SGML what the Java team had done to C++. All of the non-essential, unused, cryptic parts of SGML were sliced away. What remained was a lean, mean marking up machine: XML. The specification of XML (written mostly by Tim Bray and C.M. Sperberg-McQueen) was only 26 pages as opposed to the 500+ pages of the SGML specification! Nevertheless, all the useful things which could be done by SGML, could also be done with XML.

Over the next few years, XML evolved, drawing from the work of its sponsors and the work of developers solving similar problems such as Peter Murray-Rust who had been working on CML (Chemical Markup Language) and the consortium of folks working on MathML. By mid 1997 The eXtensible Linking Language XLL project was underway and by the summer of 1997, Microsoft had launched the Channel Definition Format (CDF) as one of the first real-world applications of XML.

Finally, in 1998, the W3C approved Version 1.0 of the XML specification and a new language was born.

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