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RE: Casting to types derived from xs:NOTATION

From: Caroline Rioux <crioux@decisionsoft.com>
Date: Wed, 13 Aug 2003 10:43:49 +0100 (BST)
To: Ashok Malhotra <ashokma@microsoft.com>
cc: "public-qt-comments@w3.org" <public-qt-comments@w3.org>
Message-ID: <Pine.LNX.4.44.0308131036350.20517-100000@ouse.dsl.local>

Thanks for the quick reply,

[I am looking at the latest public version of F&O, 2003-05-02]

I understand that you cannot construct xs:NOTATION, but it is not clear to 
me from the specs that this applies to all types *derived* from 
xs:NOTATION.  Are they dissallowed as well?

I think this should be made clearer, since in the casting table we are 
allowing casts from xs:NOTATION to xs:NOTATION, which implies that there 
is some way to get a hold of a value of type xs:NOTATION or derived from 
it.

Thanks again,
Caroline

On Tue, 12 Aug 2003, Ashok Malhotra wrote:

> Caroline:
> Which version of the F&O are you looking at?  The latest version
> disallows both constructing xs:NOTATION and casting to it.  I think this
> is the right decision given the context dependent nature of the
> datatype.
> 
> All the best, Ashok
> 
> > -----Original Message-----
> > From: public-qt-comments-request@w3.org [mailto:public-qt-comments-
> > request@w3.org] On Behalf Of Caroline Rioux
> > Sent: Tuesday, August 12, 2003 9:36 AM
> > To: public-qt-comments@w3.org
> > Subject: Casting to types derived from xs:NOTATION
> > 
> > 
> > Hi,
> > 
> > I have two questions regarding xs:NOTATION.
> > 
> > 1. Does there exist a constructor my:notation(xdt:anyAtomicType) for
> > my:notation derived by restriction from xs:NOTATION?
> > 
> > From F&O 5.2 'Constructor Functions for User-Defined Types':
> > 
> > "For every globally-defined atomic type in the static context (See
> [XQuery
> > 1.0: An XML Query Language] that is derived by restriction from a
> > primitive type, there is a constructor function [...] whose effect is
> to
> > create a value of that type from the supplied argument"
> > 
> > However F&O 17.15 Casting to xs:NOTATION states:
> > 
> > "It is not possible to cast values of any other type to xs:NOTATION
> > because the validity of an xs:NOTATION value is context dependent and
> > cannot, in general, be determined."
> > 
> > This appears inconsistent since, according to F&O 5.1, constructors
> are
> > equivalent to casting.
> > 
> > 2.  If constructors for types derived from xs:NOTATION exist, how do
> > they work?
> > 
> > According to F&O 17.5:
> > 
> > "Casting across the type hierarchy is logically equivalent to three
> > separate steps performed in order. Errors can occur in either of the
> > latter two steps.
> > 
> > * Cast the source value, up the hierarchy, to the primitive type of
> the
> > source.
> > * Cast the value to the primitive type of the target type.
> > * Cast the value down to the target type. "
> > 
> > In the case of xs:NOTATION however:
> > 
> > xs:string("http://example.com:jpeg") cast as my:notation
> > 
> > (where my:notation is derived by restriction from xs:NOTATION)
> > 
> > should be allowed (see XPath 2.0 Language 3.10.2 4.3), but the second
> step
> > above would fail, since casting from xs:string to xs:NOTATION is not
> > permitted.
> > 
> > Thanks for any clarifications,
> > Caroline
> > 
> > --
> > Caroline Rioux, Software Engineer           +44-1865-203192
> > DecisionSoft Limited
> http://www.decisionsoft.com
> > XML Development and Services
> > 
> > 
> > 
> > 
> 
> 
> 

-- 
Caroline Rioux, Software Engineer           +44-1865-203192
DecisionSoft Limited                        http://www.decisionsoft.com
XML Development and Services
Received on Wednesday, 13 August 2003 05:33:38 UTC

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