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[Bug 15791] New: [XQ30] XQST0054

From: <bugzilla@jessica.w3.org>
Date: Mon, 30 Jan 2012 12:05:34 +0000
To: public-qt-comments@w3.org
Message-ID: <bug-15791-523@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=15791

           Summary: [XQ30] XQST0054
           Product: XPath / XQuery / XSLT
           Version: Member-only Editors Drafts
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XQuery 3.0
        AssignedTo: jonathan.robie@gmail.com
        ReportedBy: tim@cbcl.co.uk
         QAContact: public-qt-comments@w3.org


In XQuery 3.0:

"If the initializer of a variable V depends on V, a static error is raised
[err:XQST0054]"

I believe that the existance of fn:function-lookup may mean it is possible to
construct a query in which a variable depends on itself, but that this cannot
be determined statically.

Suppose the existance of a document 'some.xml' with root element functionQName
of type xs:QName with value 'local:return-v'.  The following query shows how
the initializer of $v might dynamically depend on $v.

declare variable $v := function-lookup(doc('some.xml')/functionQName, 0)();

declare function local:return-v()
{
  $v
};

$v

I suggest making this error a dynamic error, as it is in XSLT:

[Definition: A circularity is said to exist if a construct such as a global
variable ... is defined in terms of itself. ... ]

[ERR XTDE0640] In general, a circularity in a stylesheet is a non-recoverable
dynamic error. However, as with all other dynamic errors, an implementation
will signal the error only if it actually executes the instructions and
expressions that participate in the circularity. Because different
implementations may optimize the execution of a stylesheet in different ways,
it is implementation-dependent whether a particular circularity will actually
be signaled.

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Received on Monday, 30 January 2012 12:05:38 UTC

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