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[Bug 4242] Static typing of name tests

From: <bugzilla@wiggum.w3.org>
Date: Wed, 17 Jan 2007 08:31:41 +0000
CC:
To: public-qt-comments@w3.org
Message-Id: <E1H76Cr-0002No-EZ@wiggum.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=4242

           Summary: Static typing of name tests
           Product: XPath / XQuery / XSLT
           Version: Candidate Recommendation
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Formal Semantics
        AssignedTo: simeon@us.ibm.com
        ReportedBy: jens.teubner@in.tum.de
         QAContact: public-qt-comments@w3.org


Hi Jerome,

correct me if I am wrong, but I think there is a problem with the static type
inference rules in Section 8.2.3.1.1 (Name Tests).

Consider the expression

  $v/self::foo

and $v has the static type `element *' (we know it's exactly one element, but
we don't know its name).

The Formal Semantics essentially depends on two judgments to derive the result
type of this expression:

  axis self:: of element * : element *      (Sect. 8.2.2.1.2)

then

  test foo with element of element * : element foo .

The latter is a rule in Section 8.2.3.1.1 where we perform a (non-wildcard)
name test on an element type with a wildcard name:


--------------------------------------------------------------------------------
 test QName2 with element of element * OptTypeSpec : element QName2 OptTypeSpec

I think a `?' occurrence indicator is missing here.  If $v in the above example
is a `foo' element, the result type is indeed `element foo'.  But if $v carries
a different name (say, `bar') the path step will return the empty sequence
(which would not be permitted by the above static typing rule).

The same problem arises also in some of the remaining judgments in Section
8.2.3.1.1.
Received on Wednesday, 17 January 2007 08:31:55 UTC

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