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However, awesome
XML
is, there are some drawbacks which have hindered
it from gaining widespread use since its inception. Let's
look at the biggest drawback: The lack of adequate processing
applications.
For one, XML requires a processing application. That is,
the nice thing about
HTML
was that you knew that if you wrote an HTML document, anyone,
anywhere in the world, could read your document using Netscape.
Well, with XML documents, that is not yet the case. There
are no XML browsers on the market yet (although the latest
version of IE does a pretty good job of incorporating
XSL
and
XML
documents provided HTML
is the output).
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"While it's true that browser support is limited, IE 5 and
Netscape 5 are expected to fully support XML. Also, W3C's Amaya browser
supports it today, as does the JUMBO browser that was created for
the Chemical Markup Language.
XML isn't about display -- it's about structure. This has implications
that make the browser question secondary. So the whole
issue of what is to
be displayed and by what means is intentionally left to other
applications. You can target the same XML (with different XSL) for
different devices (standard web browser, palm pilot, printer, etc.).
You should not get the impression that XML is useless until browsers
support it. This is definitely not true -- we are using it at NASA in
ways where no browser plays any role." - Ken Sall
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Thus, XML documents must either be converted into HTML before
distribution or converting it to HTML on-the-fly by middleware.
Barring translation, developers must code their own processing
applications.
The most common tactic used now is to write parsing routines in
DHTML or
Java, or Server-Side
perl
to parse through an
XML
document, apply the formatting
rules specified by the style sheet, and "convert" it all to HTML.
However, this takes some magic and the amount of work necessary
even to print "hello world" are sometimes enough to
dissuade developers from adopting the technology.
Nevertheless, parsing algorithms and tools continue to improve over time
as more and more people see the long-term benefits of migrating their
data to XML. The backend part of XML will continue to become simpler and
simpler. Already Internet Explorer and Netscape provide a decent amount
of built in XML parsing tools.
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