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[Bug 4913] Revise incomparability story to account for XPath evaluation

From: <bugzilla@wiggum.w3.org>
Date: Fri, 03 Aug 2007 19:14:27 +0000
To: www-xml-schema-comments@w3.org
Message-Id: <E1IH2bT-0006Ee-JY@wiggum.w3.org>


           Summary: Revise incomparability story to account for XPath
           Product: XML Schema
           Version: 1.1 only
          Platform: Macintosh
        OS/Version: All
            Status: NEW
          Keywords: needsDrafting
          Severity: normal
          Priority: P2
         Component: Datatypes: XSD Part 2
        AssignedTo: cmsmcq@w3.org
        ReportedBy: cmsmcq@w3.org
         QAContact: www-xml-schema-comments@w3.org

Section 2.2.3 of Datatypes reads in part:

    The value spaces of primitive datatypes are abstractions, 
    which may have values in common.  In the order relation 
    defined herein, these value spaces are made artificially 
    ·incomparable·.  For example, the numbers two and three 
    are values in both the precisionDecimal datatype and the 
    float datatype.  In the order relation defined herein, 
    two in the decimal datatype and three in the float datatype 
    are incomparable values.  Other applications making use of 
    these datatypes may choose to consider values such as these 

There may be other passages which also assert or entail the proposition
that for purposes of schema-validity assessment no comparisons of values
from different primitive types are ever necessary, or that such comparisons
always return false, etc.

While true of XSDL 1.0 and of many parts of XSDL 1.1, such claims are
no longer true of all parts of XSDL 1.1.  In XPath expressions used to
formulate assertions or conditional type assignment, values of
different primitive types are not necessarily incomparable:  the XPath
type coercion rules make some of them comparable.  And since XPath
evaluation is now (within limits) part of schema-validity assessment,
the distinction drawn in the text between 'incomparable for schema
purposes' and 'possibly comparable in other contexts, not our problem'
needs to be reformulated.

Since the WG has agreed in principle on the state of affairs we want,
I'm setting the status keyword here to needsDrafting, not 
Received on Friday, 3 August 2007 19:14:29 UTC

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