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Re: Inheritance

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 22 Oct 2001 11:51:24 +0100
To: "Tim Galle" <timgalle@cyberdude.com>
Cc: <xmlschema-dev@w3.org>
Message-ID: <f5b7ktokkwj.fsf@cogsci.ed.ac.uk>
"Tim Galle" <timgalle@cyberdude.com> writes:

> Hello everyone,
> Is the following possible with XML-schemas:
> 
> In Schema A I define a structure (element construction) and 2 kinds of
> attributes: a kind that can not be redefined (Final) and one that can be
> redifined (Overridable)
> 
> Now Schema B must take everything from A, structure and attributes.  It may
> extend the structure with new elements, and add new attributes to elements
> defined in A.  It may redefine overridable attributes from A (Polymorhing),
> but it may not redefine final attributes.

In brief, yes, you can do this.

You have to do it attribute-by-attribute, however:

A:
<xs:schema targetNamespace="urn:foo1" xmlns:my="urn:foo1">
 <xs:complexType name="struct1">
  <xs:sequence>
    ...
  </xs:sequence>
  <xs:attribute name="final1" type="my:ft1"/>
  <xs:attribute name="final2" type="my:ft2"/>
  <xs:attribute name="final3" type="my:ft3"/>
  <xs:attribute name="over1" type="xs:decimal"/>
  <xs:attribute name="over2" type="xs:string"/>
 </xs:complexType>
 
 <xs:simpleType name="ft1" final="#all">
  <xs:restriction base="xs:decimal"/>
 </xs:simpleType>
 
 <xs:simpleType name="ft2" final="#all">
  <xs:restriction base="xs:string"/>
 </xs:simpleType>
 
 <xs:simpleType name="ft3" final="#all">
  <xs:restriction base="xs:boolean"/>
 </xs:simpleType>
</xs:schema>

<xs:schema targetNamespace="urn:foo2" xmlns:core="urn:foo1"
           xmlns:ym="urn:foo2">
 <xs:import "urn:foo1"/>

 <xs:complexType name="extStruct1">
  <xs:complexContent>
   <xs:extension base="core:struct1">
     <xs:sequence>
      . . .
     </xs:sequence>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>

 <xs:element name="xyzzy">
  <xs:complexType>
   <xs:complexContent>
     <xs:restriction base="ym:extStruct1">
      <xs:attribute name="over1" type="xs:integer"/>
     </xs:restriction>
   </xs:complexContent>
  </xs:complexType>
 </xs:element>
</xs:schema>

This is OK.  If you tried to restrict "final1" instead of "over1",
you'd get an error.

Hope this helps,

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, 22 October 2001 06:50:38 GMT

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