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RE: [xml-dev] which xml schema tools do it right concerning including attributes xml:lang and xml:space

From: Dare Obasanjo <dareo@microsoft.com>
Date: Fri, 19 Apr 2002 11:14:33 -0700
Message-ID: <8BD7226E07DDFF49AF5EF4030ACE0B7E05573CBC@red-msg-06.redmond.corp.microsoft.com>
To: "Stanley Guan" <stanley.guan@oracle.com>, "Henry S. Thompson" <ht@cogsci.ed.ac.uk>
Cc: <xmlschema-dev@w3.org>
> ----- Original Message -----
> From: "Henry S. Thompson" <ht@cogsci.ed.ac.uk>
> To: "Dare Obasanjo" <dareo@microsoft.com>
> Cc: "Paul Hermans" <paul_hermans@protext.be>; 
> <xml-dev@lists.xml.org>; <xmlschema-dev@w3.org>
> Sent: Friday, April 19, 2002 2:27 AM
> Subject: Re: [xml-dev] which xml schema tools do it right 
> concerning including attributes xml:lang and xml:space
> (snip)
> >
> > XSV does the same, i.e. it only fetches one schema document per 
> > imported namespace, regardless of how many <import> elements it 
> > encounters.
> Does this mean when you import a specific namespace, you need 
> to specify the top schema document.

This seems like the wisest thing to do and is not unreasonable given that there is the <xs:include> element. 

> For example, if you try to import two schema documents in the 
> same namespace, only the first import succeeds even the 
> second document does contain additional type definitions or 
> element declarations.
> So, for the given example, people should use a proxy to 
> contain both documents and provide it to the schema processor 
> via the "import" schema component.  Am I right about this?

Or one document can <xs:include> the other which is standard operating practice for schema authors. 

> The point I try to bring up with is:
>    Should the schema processor decide whether to fetch a
>    schema document based on:
>      i) namespace only, or
>     ii) schemaLocation and namespace?

The W3C XML Schema recommendation mentions how to treat schemaLocation in <xs:import>: 

"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."

so only the first import matters since schemaLocation is ignorable anyway. 

Secondly the rules for locating schemas given a location are covered here 


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Received on Friday, 19 April 2002 14:15:49 UTC

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