xml-dev - Re: XML Schemas: <all> + extension = ?

[ht@cogsci.ed.ac.uk (Henry S. Thompson)]

"Roger L. Costello" <costello@mitre.org> writes:

> Hi Folks,
> 
> I am wishing to create a complexType which extends a base type.  I would
> like for the resulting set of elements to be unordered (using <all>).  
> 
> Here's an example to demonstrate what I mean.  Suppose that I have a
> base type called appliance, and the elements in this base type are
> unordered:
> 
> <complexType name="appliance">
>     <all>
>         <element name="description" type="string" maxOccurs="1"/>
>         <element name="warranty" type="string" maxOccurs="1"/>
>     </all>
> </complexType>
> 
> Now I would like to create another type, juiceAppliance, which extends
> appliance.  Further, I would like for the resulting set of elements to
> be unordered.  Here was my first attempt at doing this:

Can't be done as the design stands.  Derived types observe one of two
invariants:

restriction) all members of derived type are members of base type
extension) all members of derived type contain members of base type as 
           a prefix.

If we provided for your use case that would break the second
invariant.

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/

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