|
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.
|
