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[Bug 4034] don't keep superseded facets

From: <bugzilla@wiggum.w3.org>
Date: Mon, 04 Dec 2006 16:47:20 +0000
CC:
To: www-xml-schema-comments@w3.org
Message-Id: <E1GrGyO-0005Rl-Pj@wiggum.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=4034

           Summary: don't keep superseded facets
           Product: XML Schema
           Version: 1.1 only
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Structures: XSD Part 1
        AssignedTo: cmsmcq@w3.org
        ReportedBy: davep@iit.edu
         QAContact: www-xml-schema-comments@w3.org


>From Structures, 3.15.6, Schema Component Constraint: Simple Type Restriction
(Facets):

     3 The facets of R [the restriction] [must] Ěconstitute a
        restrictionĚ of the {facets} of B [the base] with respect
        to S [a set of new facets].

Within the definition of "constitute a restriction", the governing clause is:

     2 Every facet in B is in R unless it is of the same kind
        as some facet in S.

If we interpret "unless" to mean that the facet in B is prohibited if is is of
the same kind as some facet in S, then reading back into the Constraint we find
that the constraint precludes a facet of B from being also a facet of R if
there is a facet of the same kind in S.

This needs to be made clear; "unless" can also be interpreted as making no
statement about whether a facet B is in R if it is of the same kind as some
facet in S.  Recommend "unless it is of the same kind as some facet in S" be
changed to read "if and only if it is not of the same kind as some facet in S".

Since this is what is needed to resolve Datatypes bug 2246, and 2246 blocks
Structures bug 2781, this change might impact the resolution of 2781.
Received on Monday, 4 December 2006 16:47:29 GMT

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