Complex Type extension

I've got a schema which XMLSpy used to say is valid but in 4.3 says is
invalid (well, it validated in the Schema view but not in the other
views). I think XSV validates it, but I don't understand it's output
half the time so who knows.

I have a ComplexType which contains an Attribute called Logic which is
required. I need to re-use this ComplexType elsewhere but make the
Logic attribute optional.

Here's my code:

<xs:element name="CheckGroup">
        <xs:complexType>
                <xs:complexContent>
                        <xs:extension base="CheckGroupType">
                                <xs:attribute name="Logic" type="xs:string" use="optional"/>
                        </xs:extension>
                </xs:complexContent>
        </xs:complexType>
</xs:element>


Is this in fact invalid, and is there another way to acheive this
other than just making a new ComplexType?

-- 
May the flares be with you,
 Kevin                    xmldude@burieddreams.com

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