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).
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.
"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
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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