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RE: Can XML Schemas do this?

• To: "'Bryce K. Nielsen'" <bryce@s...>, "'xml-dev'" <xml-dev@l...>
• Subject: RE: Can XML Schemas do this?
• From: "Alessandro Triglia" <sandro@m...>
• Date: Tue, 21 Jan 2003 13:31:03 -0500
• Importance: Normal
• In-reply-to: <009f01c2c179$1ca7ae70$34121eac@beakon>

> -----Original Message-----
> From: Bryce K. Nielsen [mailto:bryce@s...] 
> Sent: Tuesday, January 21, 2003 13:16
> To: 'xml-dev'
> Subject: Re:  Can XML Schemas do this?
> 
> 
> > Highly application-dependent.
> >
> > <procedure><name>Replace Part#13316 in Boeing 777 Wing</name>
> >    <steps>
> >      <step>Ensure electrical systems are inactive per 
> testID 32297</step>
> >      <step>Ensure no fuel vapor concentrations per testID 
> 35151</step>
> >      <step>Open hatch and stick your head inside</step>
> >      </steps>
> >    </procedure>
> >
> > Sometimes order matters -Tim
> >
> 
> I'm not saying that explicit ordering should be removed, I'm 
> just saying that schema languages should allow both. It gives 
> me a bad taste in my mouth to tell my partners that while the 
> ordering of the nodes doesn't really matter, in order for the 
> document to validate against my schema it has to be in 
> tell-tell order.
> 
> In the above case, it's a good thing those are elements, not 
> attributes, which brings the next question if Element orders 
> are enforced (at least in W3C XML Schemas), why are Attribute 
> orders not?


I don't see this as a problem.  The case is very different.  People know
that attributes are always unordered in XML 1.0, which is not true of
elements.  So people know they cannot rely on attribute order for any
purpose - it is very clear that attribute order cannot carry any
information.  On the other hand, element order does carry some
"information", at least in the sense that it has some entropy associated
with it.  This is the reason why - I believe - it is useful that a
schema imposes a fixed order whenever there is no intention to attribute
semantics to the order of elements.  That is, to prevent people from
misunderstanding (or misusing) the messages by using the extra entropy
each one in one's own way.

Alessandro Triglia


> 
> -BKN
> 
> 
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• References:
  • Re: Can XML Schemas do this?
    • From: "Bryce K. Nielsen" <bryce@s...>

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