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Re: A Plea for Schemas

• From: "Simon St.Laurent" <simonstl@s...>
• To: xml-dev@i...
• Date: Mon, 01 Nov 1999 14:23:22 -0500

At 12:31 PM 11/1/99 +0100, Matthew Gertner wrote:
>I totally agree. The idea of some kind of discovery mechanism for
>schemas has already been batted around this list (and I believe I heard
>something about some W3C activity starting in this area?). 

The more I've worked with XML, the less convinced I've become that central
repositories for schemas hold a meaningful answer to information
processing.  While access to prior work is useful for reference, learning,
and some avoidance of reinventing the wheel, I don't think the dream of
schema repositories as standards bodies makes sense.  (I used to, really!)

>Getting all
>the competing approaches behind a standard schema language is a major
>prerequisite for this.  

I'm not convinced that this is actually critical.  You can start with DTDs
or XML-Data and move around as necessary - try out XML Authority
(www.extensibility.com) for one example of a tool that makes it very easy
to convert among different schema vocabularies.  Data type information can
be stored in DTDs quite easily, for instance, and put into a schema format
when appropriate.  This approach reduces the seemingly high cost of
switching infrastructures.

Rick Jelliffe's Schematron is another interesting option, providing
supplemental tests that aren't typically included in schemas.  Multiple
schema languages may in fact provide useful tools that a single vocabulary
and structure might not easily include.

>It is hard to justify investing too much in
>schema development and infrastructure if the final form and capabilities
>of this schema language are still unclear. How and whether schemas will
>then be made available is very much up in the air. The most promising
>option I see is to create some kind of schema marketplace that will
>enable people to get their schemas out there, with the metadata
>necessary for others to find them, and let "free market" competition
>decide which schemas will gain general acceptance. There are already
>some efforts of this type, but they smack a little of marketing
>manoeuvres controlled by a single company and not real attempts to
>create an open marketplace.

It's interesting, though, that the 'marketing manoeuvres' fosters this kind
of open competition, while the more neutral body has set up a formal
process for settling on schemas through closed committees.

I'm not sold on the need for single schemas for particular markets, nor do
I think a single repository is going to make that much difference (except
perhaps for PR).  

In some cases, companies will be able to agree on industry-wide standards,
but I don't think that approach is the only path forward.  XML's
transformability (courtesy of its structures plus XSL, Omnimark, MDSAX, and
other tools) opens the door to a Babel-like world in which we have a
significant - and adquate - chance of understanding each other without
having to proceed in lockstep.

Simon St.Laurent
XML: A Primer, 2nd Ed.
Building XML Applications
Inside XML DTDs: Scientific and Technical
Sharing Bandwidth / Cookies
http://www.simonstl.com

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