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[Bug 2167] R-170: Inconsistent use of the term "derived"

From: <bugzilla@wiggum.w3.org>
Date: Wed, 14 Sep 2005 18:03:29 +0000
To: www-xml-schema-comments@w3.org
Message-Id: <E1EFbbV-0006ZT-46@wiggum.w3.org>


           Summary: R-170: Inconsistent use of the term "derived"
           Product: XML Schema
           Version: 1.0
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XSD Part 1: Structures
        AssignedTo: ht@w3.org
        ReportedBy: sandygao@ca.ibm.com
         QAContact: www-xml-schema-comments@w3.org

XML Schema Part 1 (Structure) and XML Schema Part 2 (Datatypes) seem to have 
different notions of "derived" for simple types. 

According to Part1, setion 3.14.6, Schema Component Constraint: Type Derivation 
OK (Simple), type unions and list extensions are NOT "derived" from their 
respective member types (but their member types are regarded as "derived" from 
the union type resp. list extension). 

This is in contrast to Part 2, which defines union types and list extensions 
as "derived" from their respective member types ( and 

The inconsistent semantics of "derived" can lead to confusion among schema 
authors, in particular when working with substituion groups, instance type 
overriding, and redefinitions. 

We suggest to drop the term "derived" for type unions and list extensions in 
XML Schema Part 2 and to replace it with the term "constructed". This would 
also affect the classification of the built-in types NMTOKENS, IDREFS, and 
ENTITIES, which are no longer "derived by list" but "constructed by list". 


Ashok's response:
Received on Wednesday, 14 September 2005 18:04:57 UTC

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