RE: extend two elements?

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From: "Paul Spencer" <xml-dev-list@b...>
To: "Amy Wong" <amy_wanes@y...>,<xml-dev@l...>
Date: Wed, 1 Nov 2006 11:05:08 -0000

Amy,

You do not give the definition of your "student" type.

Let me make a few assumptions:

1. Your "student" type is sufficiently complex that it is worth doing this as an extension, rather than just a separate definition (the easy way).

2. Your "student" already contains an address, and you want to replace this with the "grad_address".

You already have a reply from Jack Lindsey making different assumptions.

If my assumptions are correct, you have a slight problem as an extension cannot replace the "address" type with the "grad_address" type. I would create a new type and derive both "student" and "grad_student" from this. Let's call the abstract type "student_base", with a definition that is the same as student but without the address. Then "student" extends this by adding the "address" and "grad_student" extends it by adding the "grad_address" and the appropriate attributes.

Note that you can make it impossible to create an element based on the "student_base" type directly if you like, but this is not strictly necessary.

Regards

Paul Spencer

-----Original Message-----
From: Amy Wong [mailto:amy_wanes@y...]
Sent: 31 October 2006 19:59
To: xml-dev@l...
Subject: extend two elements?

Hi,

I have an element called "grad_student" which extends "student". Now I want to extend "grad_address" element too since "grad_student" element needs address related info. Unfortunately I cannot merge address info from "grad_address" element into "grad_student" element. I am wondering how I can
extend another element when this element already extends a base element?

regards,
    <xsd:complexType name="grad_student">
          <xsd:complexContent>
             <xsd:extension base="student">
                <xsd:attribute name="name" type="xsd:string" use="required"/>
                <xsd:attribute name="grade" type="xsd:string" use="required"/>
             </xsd:extension>
         
 </xsd:complexContent>
       </xsd:complexType>
       <xsd:element name="grad_student" type="xyz:grad_student"/>
       
          <xsd:complexType name="grad_address">
             <xsd:complexContent>
                <xsd:extension base="address"> 
                   <xsd:attribute name="state" type="xsd:string" use="required"/>
                   <xsd:attribute name="zip_code" type="xsd:string" use="required"/>
                </xsd:extension>
             </xsd:complexContent>
          </xsd:complexType>
       <xsd:element name="grad_address" type="xyz:grad_address"/>
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