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Re: [F&O] Casting to xs:NOTATION, xs:QName not clarified

From: Frank Legler <legler@sigma.informatik.hu-berlin.de>
Date: Mon, 17 Jan 2005 10:23:37 -0800
To: Laurens Holst <lholst@students.cs.uu.nl>
CC: legler@informatik.hu-berlin.de, public-qt-comments@w3.org
Message-ID: <jUsT.aNoTheR.mEsSaGe.iD.110598718110711@www.informatik.hu-berlin.de>

At Saturday, 15 January 2005, Laurens Holst <lholst@students.cs.uu.
nl> wrote:

>Frank Legler wrote:
>> Hello Ashok,
>> 
>> Does that mean that it is possible to construct xs:QName and xs:
NOTATION 
>> from xs:string,
>> but it is not possible to cast xs:QName and xs:NOTATION from a xs:
>> string?
>
> From section 17.6 of XQuery 1.0 and XPath 2.0 Functions and Operators:
>
>"Casting from xs:string and xdt:untypedAtomic to xs:QName, xs:NOTATION,

>or types derived from them is not possible because it requires knowledge 

>of the namespace context. Constructor functions are available to 
>construct values of these types provided that the lexical representation 

>is known statically."
>

I still do not understand why we differentiate between casting and 
construction here.
Given the following examples
  (1) "a" cast as xs:QName   (: invalid according to the spec :)
    and
  (2) xs:QName("a")          (: valid according to the spec :)

Don't both examples require knowledge of the namespace context? 
And why is a static evaluation possible for (2) but not for (1)?

Regards,
Frank




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Received on Monday, 17 January 2005 18:39:50 UTC

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