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Re: Mixed type fields

From: James Clark <jjc@jclark.com>
Date: Tue, 23 Jan 2001 06:49:14 +0700
Message-ID: <3A6CC6FA.6DA2FEF5@jclark.com>
To: XML Schema Comments <www-xml-schema-comments@w3.org>


"Biron,Paul V" wrote:
> 
> > -----Original Message-----
> > From: ht@cogsci.ed.ac.uk [SMTP:ht@cogsci.ed.ac.uk]
> > Sent: Monday, January 22, 2001 1:51 AM
> > To:   James Clark
> > Cc:   XML Schema Comments
> > Subject:      Re: Mixed type fields
> >
> > James Clark <jjc@jclark.com> writes:
> >
> > > What happens if fields in identity constraints evaluate to values of
> > > different types for different target node-sets? This would require be to
> > > compare values of different types.  Is this an error, always false,
> > > false only if they do not have a common super type or what?
> >
> > Should be clarified.  I _think_ (need confirmation from the Datatypes
> > editors) that values from distinct value spaces always compare not
> > equal, but that a derived type's values _are_ in the same value space as
> > its base type, so e.g.
> >
> > 3 [integer] = 3 [short]
> >
> > and "foo" [string] = "foo" [token]
> >
> Yes, that is correct.  From section "2.4.1.1 Equal" of part 2 [1]
> 
>         For any values a, b drawn from the value space,
>         Equal(a,b) is true if a = b, and false otherwise.
> 
>         By definition, given value space  A and value space B
>         where A and B are not related by restriction, for every
>         pair of values a from A and b from B, a != b.
> 
> However, looking at that I now realize I need to update the 2nd sentence to
> include derivation by union as well, since unions work the same as
> restriction as far as equality is concerned.

Makes sense.  It would be nice if Part 1 could refer to the specific
section of Part 2.

What about when the two values have different whiteSpace facets? 
Suppose I have

t1 = "x  y" [token]
t2 = "x y" [token]
s1 = "x  y" [string]
s2 = "x y" [string]

Which t/s pairs compare equal? Do I just compare the values after
whitespace normalization according to their respective whiteSpace
facets, which would imply t1 != s1, which seems a bit surprising?

James
Received on Monday, 22 January 2001 19:02:07 GMT

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