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The recent battles over HLink have left me reminiscing about some
pleasanter times, on a cruise ship, with Jon Bosak talking about the
early history of XML and how it came to be in its present form. (I was
not involved in any of these activities, so people are very welcome to
correct me.)
XML seems to have been conceived as three parts: Syntax, Styling, and
Linking. In the SGML world, these three were largely represented by
SGML itself, DSSSL, and HyTime, but all three of those were widely seen
as overly complicated and were only rarely implemented completely.
I believe Jon said something to the effect that they didn't think it
mattered which project they tackled first, but syntax turned out to be
the first project, and it became XML. The other two projects evolved
into Extensible Stylesheet Language (XSL) and Extensible Linking
Language (XLL), though XSL is more commonly referred to as XSLT and
XSL-FO (to avoid confusion with the MSXML XSL) and XLL became XLink.
All three of these have interesting trajectories, not least because
"SGML for the Web" has always seemed to have a certain lack of interest
in the HTML Web that preceded it and which continues. (All
interpretations of those trajectories from here forward are definitely
mine, not Jon Bosak's!)
XML directly on the Web seems to have fallen victim to the notion that
XML needed a transformative style approach, missing the easy opportunity
that CSS provided for document display and requiring people to use XSLT.
That notion has also provided Microsoft with plenty of cover for their
(non-)approach to XML in the browser, which may have successfully kept
XML off the ordinary Web.
XSL ran into several challenges, though it seemed to keep going its own
way regardless. The XSL community seemed, from the perspective of a CSS
user, to have little interest in and much contempt for the notion of
formatting through annotation generally and CSS particularly. The
"Formatting Objects Considered Harmful" argument may not have bothered
people who considered FOs a necessary result of a transformation, but it
certainly troubled those of us who had hoped XML would encourage the
sharing of computer-interpretable information.
XSLT came through as a powerful set of tools for developers who could
take the time to learn them - great stuff, though not something I throw
at even advanced Web developers lightly. XSL-FO sorted out differences
with CSS and finally reached Recommendation. It's great stuff for
producing print documents, but I don't think we need to worry about
FO-based "Semantic Firewalls" any time in the near future.
XLink just kind of stalled. It seemed to me that most of the XLink WG
was more interested in getting more elegant and sophisticated hypertext
than HTML provided on to the Web than in figuring out whether the Web
and its developers were actually interested in it. On xlxp-dev, simple
links were commonly described as grudging accomodations to the HTML way
of linking, and frequently cursed for complicating the underlying model
of linking.
Bill Smith described XLink at JavaOne (1999? 2000?) as "bringing
hypertext linking on the Web up to the early 1970s". For those of us
who credit HTML with bringing hypertext linking to public consciousness,
I'm not sure that the early 1970s was all that much more exciting than
1996. XLink did reach Recommendation status eventually, but to be
honest I'm not really sure why.
On the bright side, XML has certainly found use beyond traditional Web
development, and XSLT has found plenty of use in styling (mostly
generating HTML or HTML+CSS, ironically enough) and in many other
transformation situations.
There's nothing particularly to be sad about, but I think I still look
forward to "XML on the Web". Maybe this could eventually emerge from a
development style that looks more closely at what the Web does well and
what XML can add instead of piling more features into XML or creating
formats designed for usages only tenuously connected to the Web. The
REST folks seem headed in the right direction, but I hope to see more of
this in more general Web development. Though I don't think XLink was
the right answer, we still need a hypertext answer (AFs? CSS per Opera?)
to get XML on the Web.
Lots of good questions yet to answer, even after years of work.
-------------
Simon St.Laurent - SSL is my TLA
http://simonstl.com may be my URI
http://monasticxml.org may be my ascetic URI
urn:oid:1.3.6.1.4.1.6320 is another possibility altogether
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