XML Schema question on inheritance

[James Williams - Sun East Coast IR Development <James.P.Williams@Sun.COM>]

Is it possible to derive a complexType from another complexType
if they both use the <all> content group ?

Here is an example of what I want to do:

    <complexType name="parentType">
                <all>
                    <element name="x" type="string"/>
                    <element name="y" type="string"/>
                </all>
    </complexType>

    <complexType name="derivedType">
        <complexContent>
            <extension base="parentType">
                <all>
                    <element name="z" type="string"/>
                </all>
            </extension>
        </complexContent>
    </complexType>


Xerces 1.4.0  won't allow this, and I'm wondering if this is a bug, or
something the spec won't allow.

Thanks,
Jim Williams