Re: [xml-dev] RE: Is schemaLocation just a hint in schema import?

[Dan Vint <dvint@dvint.com>]

This seems another instance where the schema 
folks changed the path of the XML standard. In a 
DTD, it is the last definition read that becomes 
the definition - seems like the import rules 
should treat schemas in the same way. The only 
place that seems like it needs special handling 
is with redefine in the situation that I just got caught in.

I have Schema A that is imported into Schema B, I 
then redefine Schema A and import Schema B. This 
also seems to be a implementation dependent 
problem and the solution that was proposed but I 
haven't tested was to remove the schema location 
on the import of Schema A into schema B. I find 
it strange that some how the physical file 
location might control part of the triggering of 
this rule. Seems to me that the namespace should 
be the equivalent of specifying a file location, but maybe it isn't.

How about a push to simplify XML schema instead 
of changing the syntax and features of the core XML spec?

..dan



At 09:03 AM 10/9/2006, Michael Kay wrote:
>
> > "NOTE: The above is carefully worded so that multiple
> > <import>ing of the same schema document will not constitute a
> > violation of clause 2 of Schema Properties Correct (§3.15.6),
> > but applications are allowed, indeed encouraged, to avoid
> > <import>ing the same schema document more than once to
> > forestall the necessity of establishing identity component by
> > component.
> > Given that the schemaLocation [attribute] is only a hint, it
> > is open to applications to ignore all but the first <import>
> > for a given namespace, regardless of the ·actual value· of
> > schemaLocation, but such a strategy risks missing useful
> > information when new schemaLocations are offered."
> >
> >
> > Can anybody tell me the motivation for this note in the schema spec?
> >
>
>I've pointed out in comments on 1.1 that if the spec really were carefully
>worded, then the (non-normative) note wouldn't be needed.
>
>The spec, I think, is saying two things:
>
>(a) if you do two imports from the same schemaLocation (whatever "same"
>means) then you should be OK; the components should only be imported once.
>
>(b) if you do two imports from different schemaLocations (whatever
>"different" means) then it's pretty much undefined what happens: the system
>may import both and report any conflicts (such as the same element
>declaration appearing in both), or it may import both and detect that the
>two are actually identical, or it may import one and ignore the other.
>
>Michael Kay
>http://www.saxonica.com/
>
>
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