Bug 4151 – [XQuery] XQTY0086 description is too limited

Bug 4151 - [XQuery] XQTY0086 description is too limited

Summary:

[XQuery] XQTY0086 description is too limited

Status:	CLOSED FIXED

Product:	XPath / XQuery / XSLT
Component:	XQuery 1.0
Version:	Proposed Recommendation
Platform:	PC Windows XP

Importance:	P2 normal
Target Milestone:	---
Assigned To:	Don Chamberlin
QA Contact:	Mailing list for public feedback on specs from XSL and XML Query WGs

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Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2007-01-05 21:14 UTC by Michael Kay
Modified:	2007-03-19 22:32 UTC (History)
CC List:	1 user (show)

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Description Michael Kay 2007-01-05 21:14:55 UTC

One of my users is struggling with the problem of how to use XQuery to make an
amended copy of elements with namespace-sensitive content. It really isn't easy
(in fact, I don't think it's possible in general); but that's a subject for
vendor extensions now and for XQuery 1.1 in due course.

Meanwhile, there's a situation that the spec doesn't seem to address. Consider
the construct

element { node-name($t) } {
    $e/@*, $e/*
  }

where construction mode is preserve, and one of the attributes is typed as a
QName. I think this should give error XQTY0086. But the current description of
XQTE0086 is too narrow. It says:

<quote>
It is a type error [err:XQTY0086] in this case [where copy-namespaces mode
specifies no-preserve] if the typed value of the copied element or of any of
its attributes is namespace-sensitive.
</quote>

But in this example the namespace-sensitive attribute does not belong to a
copied element, and that's a problem regardless of the copy-namespaces mode.

The equivalent XSLT error condition is wider:

<quote>
[ERR XTTE0950] It is a type error to use the xsl:copy or xsl:copy-of
instruction to copy a node that has namespace-sensitive content if the
copy-namespaces attribute has the value no and its explicit or implicit
validation attribute has the value preserve. It is also a type error if either
of these instructions (with validation="preserve") is used to copy an attribute
having namespace-sensitive content, unless the parent element is also copied. A
node has namespace-sensitive content if its typed value contains an item of
type xs:QName or xs:NOTATION or a type derived therefrom. The reason this is an
error is because the validity of the content depends on the namespace context
being preserved.
</quote>

I think this needs a new clause, perhaps between D and E, along the lines:

<proposed>
D2 If construction mode is preserve, and the value of an enclosed expression
includes an attribute node whose typed value is namespace-sensitive, then error
[err:XQTY0086] is raised.
</proposed>

Comment 1 Hans-Juergen Rennau 2007-01-09 22:56:13 UTC

Probably the only way out, but the implied restriction is a pity: a general
impossibility to incorporate detached namespace-sensitive attributes during
construction. 

An alternative which comes to mind is probably unacceptable, but let me
nevertheless describe it: to accept the attribute without error IF the in-scope
namespaces of the receptor element include a namespace binding matching the
namespace binding implied by the QName/Notation value. Thus one could "prepare"
the receptor, if necessary. An obvious problem however would be that the
receptor's namespace bindings themselves are only finalized by analyzing the
attributes (3.7.4). Thus we would get an unpleasant mixture: some attributes
creating namespace bindings, and others requiring them.

Comment 2 Jim Melton 2007-02-26 00:34:33 UTC

The fix for this bug does not appear in the Recommendation of 23 January 2007. 
It will be considered for a future publication (either an Errata document or
some possible future version of the specification).

Comment 3 Don Chamberlin 2007-03-19 22:31:25 UTC

Michael,
The Query Working Group has discussed your comment and agreed to add a new rule
in Section 3.7.1.3, following the current Rule 1.e.ii.D, as follows: 

An enclosed expression in the content of an element constructor
may cause one or more existing nodes to be copied. Type error XQTY0086
is raised if:

(a) An element node is copied, and the typed value of the element node
or one of its attributes is namespace-sensitive, and construction mode
is preserve, and copy-namespaces mode is no-preserve. 

(b) An attribute node is copied but its parent element node is not
copied, and the typed value of the copied attribute node is 
namespace-sensitive, and construction mode is preserve.

(NOTE: Explanation of XQTY0086: It is
not possible to preserve the type of a QName without also preserving
the namespace binding that defines the prefix of the QName.)

This new rule (and related editorial changes) will appear in a future XQuery
errata document.

Since you were present for the discussion of this bug report, I have marked the
report as Fixed and Closed.

Regards,
Don Chamberlin (for the Query Working Group)