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   RE: [xml-dev] XML Schema considered harmful?

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G'day Rick.

> > I've probably completely missed the point here, but doesn't an 
> XML Schema
> > that only has one global element achieve the above? Maybe its a 
> matter of
> > semantics but that's how it's panned out in practice for me thus far.
> But then you cannot use subsititution groups:  this is the kind 
> of complexity 
> that James is talking about I think--the complexity when using one
> feature makes another disappear arbitrarily. 

My point was in the context of the statement made by James which used 
the words "there is no way". There is a way. I acknowledge the 
side effect. I have always tended to use type rather than element 
definitions in schemas so have not used substitution groups much. 

> Were these projects IETF protocols? and  are you are an XML or schema
> expert or, as we can expect IETF people to be,  are you only using XML 
> because it will be more convenient than rolling your own syntax and you
> are not an expert?   If I were developing a protocol, I would be
> take some convincing that XML Schemas was not overkill for my
> requirements.   

In my case, it was a matter of what the communicating organisations could
commercially get within each of their IT infrastructures. We wanted both 
structural and content validation. We started two years ago. 

When (?if) RELAX NG appears in MSXML, the choice will be greater. 

> > James is emphatic, and that is only natural, but his arguments paint
> > issues as black and white (XML Schema = bad, RELAX NG = good) and my
> > experience with XML Schema suggests shades of grey.
> But it is not James who is being black and white: it is the draft 
> RFC wanting to 
> ban the use of RELAX NG! (and, Schematron or the DSDL effort for 
> that matter!)

I was meaning more in terms of his portrayal of the limitations of XSD.

> It would make more sense for the RFC to merely say something like
> this
> "Standard schema languages (E.g. ISO RELAX NG or W3C XML Schemas)
> should be used in preference to proprietary or non-standard languages. 
> Schema languages should be used conservatively: exotic or difficult or 
> badly-described features may be badly implemented or used incorrectly 
> or be difficult to diagnose."

If you have the choice of two books in English, or one in English and
one in a language which you didn't know, which would you choose? 
I know which I'd prefer :-)



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