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[Bug 2846] RQ-142 Are non-required PSVI properties forbidden? (PSVIProp)

From: <bugzilla@wiggum.w3.org>
Date: Sat, 11 Feb 2006 01:42:31 +0000
To: www-xml-schema-comments@w3.org
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Message-Id: <E1F7jmR-0005Bq-Lb@wiggum.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=2846

           Summary: RQ-142 Are non-required PSVI properties forbidden?
                    (PSVIProp)
           Product: XML Schema
           Version: 1.1 only
          Platform: Other
        OS/Version: All
            Status: NEW
          Keywords: needsDrafting
          Severity: normal
          Priority: P2
         Component: Structures: XSD Part 1
        AssignedTo: ht@w3.org
        ReportedBy: cmsmcq@w3.org
         QAContact: www-xml-schema-comments@w3.org


This issue was originally reported by Lisa Martin.

There are various statements in the spec of the form:

    If some condition, x, is true, then, in the post-schema-validation
    infoset it has the properties a,b,c ...

For example:

    If an element is valid with respect to a type definition, as per
    Element Locally Valid (Type), in the post-schema-validation
    infoset the item has a property ...

    Furthermore, the item has one of the following alternative
    sets of properties:

       [type definition]
       ... 

Is it true that if condition x does *not hold*, then the processor is
*not permitted* to include properties a,b,c in the PSVI, even if such
information is available? I'm assuming this is what was intended,
based on the clarifications drafted for the Query WG on the topic of
PSVI.

If this is the case, should the Structures spec clarify this?
...perhaps with wording similiar to: "The properties a, b, c are in
the PSVI if and only if ..."

As an aside, wouldn't it be useful to get at type information for an
element that was not valid, if the processor had that information?

This item was discussed in the meeting of 2004-03-25
(http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2004Mar/0133.html).
Three points were identified as close to consensus:

  1 We should eliminate any dependency on the absence of specific
    properties (i.e. important situations should be describable
    and distinguishable in terms of properties and their values,
    without appeal to the absence of particular properties), or if
    this proves unfeasible in particular cases we should say 
    explicitly that a property is present "if and only if" certain
    conditions apply.  Any remaining "if" (if any) would be a
    true conditional, not an equivalence.

  2 Any specification of a class of processors (including ours) can
    require specific additional information not in the PSVI, though
    should note that interoperability is better if applications depend
    only on the properties present in the PSVI as we define it.

  3 In our own specification of processor classes, we should be
    explicit that processors may provide additional information.
    (Or alternatively be explicit that they must not -- but the
    chair believes the WG consensus was to allow it.)

This item was discussed in the meeting of 2004-04-01
(http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2004Apr/0003.html).
Phase 1 agreement was reached on point 1 above.  The other two points
were moved to RQ-144.
Received on Saturday, 11 February 2006 01:42:39 UTC

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