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   Re: [xml-dev] Restrictions on existence of attributes?

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Stan Kitsis wrote:

> Relax NG is not the best way to solve these kinds of problems.  We
> know about the problems listed above because Xml Schema and various
> processors have been extensively tested and used in real world.  A
> lot of corner cases were found and software was adjusted to handle
> them.  

Weren't such corner cases caused by a lack of formal underpinning and 
complexity of XSD spec?

> today than they were a year or two ago.  I don't know if various
> Relax NG engines have gone through similar real world usage and
> cleanup.  How confident are you that if Howard starts using Relax NG,
> he wouldn't be in the same situation?  

RELAX NG specification is very short and doesn't contain "dark corners" 
compared to XSD specs. RELAX NG is based on formal model of hedge 
grammars and validation is defined very formally, thus leaving no space 
for different interpretations by different implementations. Given the 
DTD, XSD and RELAX NG, RELAX NG is able to express more document 
structures then two other languages.

> Also, does RELAX NG have
> enough conformant implementations on different languages and
> platforms to make data defined with RELAX NG truly portable?  XSD has
> a lot of problems, but it is fairly ubiquitous.

It is ubiquitous because every Joe programmer (no offense meant) has 
support for it in his IDE from one of big software vendors who invested 
big amount of money to implement XSD support.

> JXML's main advantage
> over other data representation formats is the fact that it is
> supported by all vendors on all platforms, and that's XSD's practical
> advantage over RELAX NG, even if one acknowledges that it is better
> suited than XSD for this particular problem.

It is time to say that XSD was designed to describe unambiguous mapping 
between XML instances and data-types which was needed to support 
XML<->object and XML<->database mappings in software packages from big 
vendors. But for capturing arbitrary XML structures XSD is really 

So if you are using XML mainly as a serialization of object or 
relational data, you can live quite happily with XSD. But once you need 
more flexible document structures, or you need to develop highly modular 
and customizable schema, you will have very hard times with XSD.


   Jirka Kosek     e-mail: jirka@kosek.cz     http://www.kosek.cz
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