The forthcoming browsers from Microsoft and Netscape are the first
indications of what's going to come in the next year or so to transform XML from
today's hyped technology into the basic structural basis for data in the future.
Last time we looked at the most general level of XML support in Navigator 4.5
and Internet Explorer 5.0. This time we're going to take a look at a pair of
interesting proposals to bring a new level of abstraction to the developer
process.
The set of technologies emerging from the World Wide Web Consortium (W3C)
imply a development methodology that is core to understanding why XML is
important. That methodology depends on keeping a document's structure separate
from its presentation and both of these separate from any programmatic tricks
used to manipulate how the document will behave in response to user interaction.
The advantages to this approach are clear and emerge precisely out of the
environment in which the W3C was formed. By keeping all of these things
separate, a document can be displayed somehow, regardless of the capabilities of
the device or application being used at the client. It also means that documents
do not have to be rewritten when a new kind of application or device emerges
which means that data can live forever. This is fairly easy to understand when
talking about how a document is going to look, since we already have to deal
with the problem of display incompatibilities between different versions of IE
and Navigator and even different capabilities with the same browser running on
different operating systems.
But the problem of programmatic abstraction is a little harder to grasp than
assigning presentation attributes to document elements via CSS. The current
approach to this has been to punt to the Document Object Model (DOM), which
means that while manipulation of the document is hand-coded for each different
application based on a standard set of document interfaces, at least the
document itself remains the same. This is a good start, but it doesn't really
answer the needs of teams of developers building complicated applications that
change frequently.
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