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Re: Derivation by Extension: {content type} of {base type definition}

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 12 Feb 2001 11:16:07 +0000
To: Helena Cavanagh <helena.cavanagh@usa.net>
Cc: www-xml-schema-comments@w3.org
Message-ID: <f5b66igxibs.fsf@cogsci.ed.ac.uk>
Helena Cavanagh <helena.cavanagh@usa.net> writes:

> Dear editors,
> 
> In Part 1, clause 4.3.3, tableau "Complex Type Definition with Complex Content
> Schema Component", the definition of {content type} for the EXTENSION case
> assumes that the {base type definition} has either a {content type} that is
> empty (2.2) or that it has a particle (therefore is a pair of (content model,
> mixed|element-only)) (2.3).
> 
> This is also implicit in "Constraint on Schemas: Derivation Valid
> (Extension)", Clause 5.11, when it says:
> "1.1.4 (...) and either the {content type} of the {base type definition} must
> be empty or  
> (...) 1.1.4.2 the particle of the complex type definition must be a valid
> extension of the {base type definition}'s particle, as defined in Particle
> Valid (Extension) (5.10). "
> 
> 
> 
> Can't the {content type} of the {base type definition} be a simple type
> definition? Isn't the following possible? (it is validated by XML Spy, though
> that is no guarantee)

Yes, but that's covered by the "Complex Type Definition with _Simple_
Content" case further up.

> <xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">
> 
> 	<xsd:complexType name="aType">
> 		<xsd:simpleContent>
> 			<xsd:extension base="xsd:string"/>
> 		</xsd:simpleContent>
> 	</xsd:complexType>
> 	<!-- {content type} is a simple-type definition (that of xsd:string) -->
> 
> 
> 	<xsd:complexType name="anotherType">
> 		<xsd:complexContent>
> 			<xsd:extension base="aType">
> 				<xsd:all>
> 					<xsd:element name="subelem"/>
> 				</xsd:all>
> 			</xsd:extension>
> 		</xsd:complexContent>
> 	</xsd:complexType>
> 
> </xsd:schema>

This is broken -- what would it mean, a string followed by a
<subelem>?  The only form of complex content which allows text is
fully 'mixed' content.

> it is validated by XML Spy, thoughthat is no guarantee

XSV doesn't validate it, it just crashes :-(

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
Received on Monday, 12 February 2001 06:16:13 GMT

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