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inconsistent use of "derived"

From: Berthold Daum <berthold.daum@bdaum.de>
Date: Wed, 10 Jul 2002 16:52:29 -0600
Message-Id: <5.1.0.14.1.20020710165226.02806ec0@localhost>
To: W3C XML Schema Comments list <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 (2.5.2.2 and 
2.4.2.3).

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".

Berthold Daum
bdaum industrial communications
email: <mailto:berthold.daum@bdaum.de>berthold.daum@bdaum.de
web: <http://www.bdaum.de>www.bdaum.de
Received on Wednesday, 10 July 2002 18:57:17 GMT

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