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Hello,
although we usually try hard to keep away from personal opinions,
the danger of adopting XML Schema as the Standard for XML protocols
pressed us to break this rule.
Please find below copy of the mail we have sent to:
Date: Wed, 5 Jun 2002 10:07:08 +0200 (CEST)
From: Miloslav Nic <nicmila@systinet.com>
To: ietf-xml-use@imc.org
Subject: XML Schema and IETF protocols
Hello,
I have been alerted to this group by an xml-dev message
quoting:
4.6 Validity and Extensibility
and setting XML Schema as the high priority schema format
I would consider it a real disaster which already plagues the
current W3C standards.
I am working for Systinet, one of the top players in Web services area,
and as XML Schema is a cornerstone of Web services architecture, many of
our developers (including the best ones) have first hand experience with
both implementing schemata and with their usage in the "wild".
The experience is very frustrating:
1) I am not aware of anyone who would claim that he really understands
the specification
2) most developers cannot even read the specification and me and Jirka
Jirat are functioning as translators for them and with the very few who
can understand we often differ in interpretation which can change several
time during discussion
3) the developers in the "wild" are either using very simple constraints
correctly or a bit more complex ones in often very peculiar way (
sometimes they are using it incorrectly but often they are using it in a
way that it is very difficult to say if their construct is correct or not)
4) Several times we were asked to provide a rather basic constraints for a
document, but we were unable to do it ( we think that these constraints
cannot be expressed in XML Schema, but you can be never sure)
5) I (Miloslav Nic) tried several times to understand XML Schema but
utterly failed. I can of course use the basics and I do agree that the
primer is very useful, and I can even without big problems to use and read
part II (datatypes) , but I am unable to create mental picture of the
specification and after not seeing it for a week or two I start to read it
as an novice again.
I am founder of Zvon (http://www.zvon.org) and author of many references
and tutorials in XML field. I wrote several materials according to W3C
specifications, including several which evolved over time and sometimes
they were not easy to understand but with some perseverance I finally
succeeded. But I had to give with XML Schema, I am afraid I will be never
able to pass a beginner stage. (In comparison : I wrote Schematron
tutorial a few days after Rick Jelliffe published the original
announcement and if I need something from Relax( although thanks to Jiri
Jirat our in house expert I am not using it very often) I can figure out
what is going on in no time.
BTW: I am a coauthor of XML Schema reference (
http://zvon.org/xxl/xmlSchema2001Reference/Output/index.html ),
and had to process quite a few schemas in XML Schema (and correct some
mistakes in them so I have a proof that I have tried very hard to
understand)
6) This mail has been read by Jiri Jirat as well, so this paragraph is
authorized :
Jiri Jirat authored XML Schema 2001 and Relax NG Tutorial
(http://zvon.org/xxl/XMLSchemaTutorial/Output/index.html ) which contains
over hundred examples, some of the quite involved one, so he
definitively has some expertise in the field.
But he still has problems reading the spec and I can quite easily
recognize when he needs to find something in it as he sits next to me.
Summary:
In our personal opinion the adoption of XML Schema for IETF Standards
would have very unfortunate effects on the future and it could create
tremendous problems for everyone.
Miloslav Nic
Jiri Jirat
--
******************************************
<firstName> Miloslav </firstName>
<surname> Nic </surname>
<mail> nicmila@systinet.com </mail>
<support> http://www.zvon.org </support>
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