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[Bug 2246] R-254: Clarify merge/union of facets

From: <bugzilla@wiggum.w3.org>
Date: Wed, 14 Sep 2005 19:44:25 +0000
To: www-xml-schema-comments@w3.org
Cc:
Message-Id: <E1EFdBB-0002C5-0V@wiggum.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=2246

           Summary: R-254: Clarify merge/union of facets
           Product: XML Schema
           Version: 1.0
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XSD Part 2: Datatypes
        AssignedTo: cmsmcq@w3.org
        ReportedBy: sandygao@ca.ibm.com
         QAContact: www-xml-schema-comments@w3.org


Definition of {facets} in 4.1.2.1 Derivation by restriction: 

{facets} The union of the set of Facets (2.4) components resolved to by the 
facet [children] merged with {facets} from {base type definition}, subject to 
the Facet Restriction Valid constraints specified in Facets (2.4). 

What is being "unioned" and how does "merge" work? For example, if the base has 
a minLength facet with value 5 and the derived type has a minLength child facet 
of value 7, how many minLength facets are in the derived type's facets 
property? 

The text above makes it sound like both are present, but constraints within the 
rec strongly imply there is only one facet for each facet name. (For instance, 
reference to "*the* minLength facet" for validation constraints). Common sense 
suggests the last facet of a given name wins, but it's hard to get that 
from "union" and "merge". 

Related member-only thread: Facet equality: questions/issues
http://lists.w3.org/Archives/Member/w3c-xml-schema-ig/2004Mar/0187.html 

See
http://lists.w3.org/Archives/Public/www-xml-schema-comments/2004AprJun/0000.html
Received on Wednesday, 14 September 2005 19:44:31 GMT

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