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[Bug 4551] K-NormalizeUnicodeFunc-13

From: <bugzilla@wiggum.w3.org>
Date: Thu, 31 May 2007 09:32:09 +0000
To: public-qt-comments@w3.org
Message-Id: <E1Hth0r-0005OI-NS@wiggum.w3.org>


------- Comment #3 from tim@cbcl.co.uk  2007-05-31 09:32 -------
I'm now less convinced that

("a string", error())

is of type xs:string.  In FS 8.4

quantifier(none) = 1

The type none matches no values, therefore from the FS rules in 8.3.1 Matches
and 8.3.2 Subtyping (<:) there is no rule:

statEnv |-  error() matches none

therefore we can't apply:

statEnv |-  Value1 matches Type1
statEnv |-  Value2 matches Type2
statEnv |-  Value1,Value2 matches Type1,Type2

so we have to deduce that whatever type (xs:string, none) is, it certainly
isn't a subtype of xs:string.  All we can say is that it is of type (xs:string,
none), which is roughly xs:string+.

Therefore this test should allow for a type checking error as well as the error
thrown by error().  Quite a few of the tests use a similar construct, so will
also need to permit a type check error.

As an aside, I do find it a little strange that (Type|none) = Type _and_
quantifier(none) = 1.  It almost seems as if a type which matches no values
should have the unusual quantifier of zero.
Received on Thursday, 31 May 2007 09:32:17 UTC

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