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RE: Casting to types derived from xs:NOTATION

From: Ashok Malhotra <ashokma@microsoft.com>
Date: Wed, 13 Aug 2003 08:12:22 -0700
Message-ID: <E5B814702B65CB4DA51644580E4853FB0A3CBA58@red-msg-12.redmond.corp.microsoft.com>
To: "Caroline Rioux" <crioux@decisionsoft.com>
Cc: <public-qt-comments@w3.org>

Since this is not clear, I'll add wording saying that types derived from
xs:NOTATION as well as xs:NOTATION cannot be constructed or cast to.

All the best, Ashok

> -----Original Message-----
> From: Caroline Rioux [mailto:crioux@decisionsoft.com]
> Sent: Wednesday, August 13, 2003 2:44 AM
> To: Ashok Malhotra
> Cc: public-qt-comments@w3.org
> Subject: RE: Casting to types derived from xs:NOTATION
> 
> 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 disallowed 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 11:12:54 UTC

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