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Re: extension vs restriction

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 11 Sep 2000 09:29:44 +0100
To: "Zar Zar Tun" <zarzar@dstc.edu.au>
Cc: <www-xml-schema-comments@w3.org>
Message-ID: <f5bem2r49hj.fsf@cogsci.ed.ac.uk>
"Zar Zar Tun" <zarzar@dstc.edu.au> writes:

> What stops a person from changing the entire content of a type through the
> restricting of groups?
> Could you go like this? (which would be against the grain of derivation by
> restriction)
> 
> ...
> 
> <group name="s2r">
> <sequence>
>   <element ref='new_element' minOccurs ='0' maxOccurs='1'/>
>   <element ref='some_other_element' minOccurs ='0' maxOccurs='1'/>
> </sequence>
> </group>
> 
> <complexType name='t3' base='t2' derivedBy='restriction'>
> <sequence>
>   <group ref='s1'/>
>   <group ref='s2r'/>
> </sequence>
> </complexType>
> 
> If not, what is allowable in doing a restriction on groups and group
> components?

Sorry I wasn't clear:  groups just avoid re-typing, they don't bypass
the rules on restriction:  it's the resulting content models which
must satisfy the one-to-one mapping requirements, so your derivation
above would be ruled out.

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, 11 September 2000 04:29:47 UTC

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