<!– 3.2.3 : 2.1

One of ref or name must be present, but not both.

–> <schema xmlns=“www.w3.org/2001/XMLSchema” targetNamespace=“foo” xmlns:foo=“foo”>

<element name="bar" type="string"/>   

<element name="foo">
        <complexType>
              <sequence>
                      <element name="bar" ref="foo:bar"/>        
              </sequence>
        </complexType>    
</element>

</schema>