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Subject: RE: [relax-ng] converting relax ng schema to w3c schema?

On Thu, 2002-06-20 at 02:11, James Clark wrote:
> > On Wed, 2002-06-19 at 23:35, Michael Fitzgerald wrote:
> >> Future plans for Trang [http://www.thaiopensource.com/relaxng/trang.html]
> >> include an output module for XML Schema.
> I am implementing this at the moment.
> > The problem with this approach is that Relax NG is more "free style"
> > than W3C XML Schema and that many Relax NG schemas cannot be easily
> > translated into WXS.
> If it was easy, it wouldn't be any fun.

Sure :-)

It's not because it's difficult or complex than it's usefull though
(think of WXS for instance).
> > In other words, if you want to be compatible with both technologies, WXS
> > will be the limiting factor and you need to take it into account first.
> I don't agree.  It's the job of the user to express their intent as simply 
> and clearly as possible; RELAX NG is ideal for this.  It's the job of the 
> machine to go through all the bizarre contortions that are required to turn 
> this into a W3C XML Schema.  If the user writes something that cannot be 
> expressed in W3C XML Schema, then the machine should do what a human would 
> do: find the constructs that permits everything that they want to permit 
> and permits as few things as possible that they don't want to permit.   For 
> example, if a user wants a choice of attribute A or attribute B, then they 
> should express that intent in RELAX NG.  The machine can tell that this 
> cannot be expressed in W3C XML Schema, can inform the user of this and turn 
> it into optionally attribute A and optionally attribute B.  One could even 
> imagine it automatically generating an annotation containing a Schematron 
> rule that checked that exactly one of A and B was present.  When W3C XML 
> Schema 1.1 or 2.0 adds support for this, they will be able to take 
> advantage of this without changing their schemas.
> Completely realizing the above vision is no trivial task and the first 
> version of XSD support in Trang will fall short in many ways.  However, I 
> think it's important not to get too hung up on technical details that to 
> most users are obscure and unimportant.  Many users make relatively simple 
> use of schemas.

I guess it depends on the proportion of issues which will be raised
during the conversion (will it be rather 10% or rather 90%). And I also
guess that nobody can tell before such a tool is available...

Thanks to carry on this task!

> James
See you in San Diego.
Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
(W3C) XML Schema ISBN:0-596-00252-1 http://oreilly.com/catalog/xmlschema

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