Substituting elements in a group for the group when redefining

["Allison Bloodworth" <abloodworth@berkeley.edu>]

Hi, 

I tried to search the archives at http://lists.xml.org/archives/xml-dev/ on
this but got a message saying: The requested URL /cgi-bin/htsearch was not
found on this server. I also did a search of the internet but unfortunately
am having trouble finding info on this situation the XML Schema spec.

I would like to redefine an element (PublicEventContactType) that is defined
in a schema as containing a group called ContactInfo. I don't want to
redefine the group itself, as those changes would apply to a lot of other
elements where I don't want the change made, but just within this
PublicEventContactType element itself. You would think that this would be
something that XML Schema would support, but I am getting an error message
from XML Spy 2005 saying, "The content model of complex type
'ev:PublicEventContactType' is not a valid restriction of the content model
of complex type 'ev:PublicEventContactType' and a similar error in Oxygen
6.2. 

Is this really not possible? You would think I could substitute the elements
in the group for the group in the redefine...I do understand that I could
remove them here and put them back in in an extension, but that would
require another schema.

Original:
	<xs:group name="ContactInfo">
		<xs:sequence>
			<xs:element ref="ev:ContactName" minOccurs="0"/>
			<xs:element ref="ev:ProfessionalAffiliations"
minOccurs="0"/>
			<xs:element ref="ev:Phones" minOccurs="0"/>
			<xs:element ref="ev:EmailAddresses" minOccurs="0"/>
			<xs:element ref="ev:Addresses" minOccurs="0"/>
			<xs:element ref="ev:WebPages" minOccurs="0"/>
			<xs:element ref="ev:PreferredContactMethod"
minOccurs="0"/>
		</xs:sequence>
	</xs:group>
	<xs:complexType name="PublicEventContactType">
		<xs:sequence>
			<xs:element ref="ev:PublicEventContactID"
minOccurs="0"/>
			<xs:group ref="ev:ContactInfo" minOccurs="0"/>
			<xs:element ref="ev:PublicEventContactTypes"
minOccurs="0"/>
			<xs:element ref="ev:PublicEventContactParentID"
minOccurs="0">
		</xs:sequence>
	</xs:complexType>

Redefine:
		<xs:complexType name="PublicEventContactType">
			<xs:complexContent>
				<xs:restriction
base="ev:PublicEventContactType">
					<xs:sequence>
						<!-- REMOVING THIS ELEMENT
<xs:element ref="ev:PublicEventContactID" minOccurs="0"/> -->
						<xs:element
ref="ev:ContactName" minOccurs="0"/>
						<xs:element
ref="ev:ProfessionalAffiliations" minOccurs="0"/>
						<xs:element ref="ev:Phones"
minOccurs="0"/>
						<xs:element
ref="ev:EmailAddresses" minOccurs="0"/>
						<xs:element
ref="ev:Addresses" minOccurs="0"/>
						<!-- REMOVING THIS ELEMENT
<xs:element ref="ev:WebPages" minOccurs="0"/> -->
						<xs:element
ref="ev:PreferredContactMethod" minOccurs="0"/>
						<!-- REMOVING THIS ELEMENT
<xs:element ref="ev:PublicEventContactTypes" minOccurs="0">
						</xs:element> -->
						<!-- REMOVING THIS ELEMENT
<xs:element ref="ev:PublicEventContactParentID" minOccurs="0">
						</xs:element> -->
					</xs:sequence>
				</xs:restriction>
			</xs:complexContent>
		</xs:complexType> 

Thanks for your help,

Allison Bloodworth
Principal Administrative Analyst
Technology Program Office
University of California, Berkeley
(415) 377-8243
abloodworth@berkeley.edu