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Bug 2047 - R-181 (Structures): clarify equality and identity of lists
Summary: R-181 (Structures): clarify equality and identity of lists
Status: RESOLVED FIXED
Alias: None
Product: XML Schema
Classification: Unclassified
Component: Structures: XSD Part 1 (show other bugs)
Version: 1.1 only
Hardware: PC Linux
: P2 normal
Target Milestone: ---
Assignee: C. M. Sperberg-McQueen
QA Contact: XML Schema comments list
URL: http://www.w3.org/2001/05/xmlschema-r...
Whiteboard: datatypes cluster
Keywords: resolved
Depends on:
Blocks:
 
Reported: 2005-09-08 22:30 UTC by C. M. Sperberg-McQueen
Modified: 2008-05-31 02:44 UTC (History)
0 users

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Description C. M. Sperberg-McQueen 2005-09-08 22:30:16 UTC
See bug 2044 and bug 2045 for full description of the issue which gave
rise to this one.  

When the Working Group discussed R-181 in May 2005 (North Carolina
ftf), we instructed the editors "to correct validation rules for 
identity contraints to actually refer to identity."

It's not clear to me, at the time I add this record, whether the 
instruction applies only to 1.1 or also to 1.0.   Since equality
and identity are the same in 1.0 but not in 1.1, I suspect there may
be a need for two slightly different proposals.  For now, though,
I am concerned with fixes to the 1.1 text, so I'm entering this as
a 1.1 issue.  We can make a separate 1.0 issue if we wish, or change
this to apply to 1.0 (which means it will implicitly also apply
to 1.1).
Comment 1 C. M. Sperberg-McQueen 2007-02-23 18:36:17 UTC
On the call of 23 February 2007 the Working agreed to class this issue as
editorial.
Comment 2 C. M. Sperberg-McQueen 2007-10-14 18:09:46 UTC
At the ftf meetings of October 2007, the XML Schema WG discussed
this issue together with the XML Query and XSL WGs (in the context
of a discussion of bug 3243).

QT vigorously argued that the direction outlined for this issue in the
comments on bug 2045 and bug 2046 should be reversed and that XSDL
should align with QT in treating the difference between atomic values
and singleton lists containing those atomic values as a purely
metaphysical distinction.  After discussion, we agreed to instruct the
editors to prepare wording proposals for Datatypes (bug 2046) and
structures (bug 2047), in which it's made clear that for XSDL purposes
singleton lists are not distinguished from the atomic values which are
their list items.  As far as we could tell, this would affect only
identity constraints, since we couldn't think of any way to construct
an enumeration or a fixed value constraint which would involve
comparison of an atomic to a singleton list.  (Further thought shows
that a union of a pattern-restricted integer with a list of
differently pattern-restricted integers would allow tests to be
constructed.)

These wording proposals will, we hope, be useful in achieving
agreement on the correct technical direction.  (That is, they are
phase-1 proposals, not phase-2 proposals.)  Before we make any final
decisions, we should perform some due diligence to see if existing
processors all do the same thing in these cases (and what that thing
is) and whether existing schemas seem likely to be affected.
Comment 3 C. M. Sperberg-McQueen 2008-05-24 03:03:41 UTC
A wording proposal intended to resolve this issue is now at 

  http://www.w3.org/XML/Group/2004/06/xmlschema-1/structures.b2047.html
  (member-only link).

It should probably be read in conjunction with its companion proposal
for Datatypes at 

  http://www.w3.org/XML/Group/2004/06/xmlschema-2/datatypes.b2046.html
  (member-only link)
Comment 4 C. M. Sperberg-McQueen 2008-05-31 02:44:24 UTC
The proposals mentioned in comment #3 were adopted by the WG on today's call.
Accordingly I am marking the issue resolved.  The originator of the issue,
Stefan Wachter, has been notified by email and asked for his feedback.