I'm trying to derive a schema from a base schema.  I want to redefine
a "group" from the base schema in my derived schema in order to add
more options to the "choice" aggregate (see schema1.xsd sample).

schema1.xsd sample:
<!-- Here is a clipped down version of the group I want to redefine.
-->
<xsd:group name="INSURANCESVCRQMSGS">
   <xsd:choice>
      <xsd:element ref="HomePolicyAddRq" minOccurs="1" maxOccurs="1"/>
      <xsd:element ref="HomePolicyQuoteInqRq" minOccurs="1"
maxOccurs="1"/>
   </xsd:choice>
</xsd:group>

I'd like to redefine this "group" in the derived schema so that the
end product looks something like this:

schema2.xsd sample:
<xsd:group name="INSURANCESVCRQMSGS">
   <xsd:choice>
      <xsd:element ref="HomePolicyAddRq" minOccurs="1" maxOccurs="1"/>
      <xsd:element ref="HomePolicyQuoteInqRq" minOccurs="1"
maxOccurs="1"/>
      <xsd:element ref="MyAdditionalElement" minOccurs="1"
maxOccurs="1"/>
   </xsd:choice>
</xsd:group>

I see many examples of using the "redefine" tag to redefine a
"complexType", but I can't find anything on redefining a "group".  The
standard example for a complexType is something like the following,
which adds a new "generation" element to a "personName":

 <xs:redefine schemaLocation="v1.xsd">
  <xs:complexType name="personName">
   <xs:complexContent>
    <xs:extension base="personName">
     <xs:sequence>
      <xs:element name="generation" minOccurs="0"/>
     </xs:sequence>
    </xs:extension>
   </xs:complexContent>
  </xs:complexType>
 </xs:redefine>

Can anyone enlighten me as to what a group redefinition should look
like?

Thanks,
Bill