<xsd:simpleType name="IdentifierGenerationOptionType">
    <xsd:restriction base="xsd:string">
        <xsd:enumeration value="UseExisting">
            <xsd:annotation>
                <xsd:documentation>
                  The UseExsiting value indicates that WFS should not
                  generate a new feature identifier for the feature
                  being inserted into the repositry.  Instead, the WFS
                  should use the identifier encoded if the feature.  
                  If a duplicate exists then the WFS should raise an
                  exception.
               </xsd:documentation>
            </xsd:annotation>
        </xsd:enumeration>
        <xsd:enumeration value="ReplaceDuplicate">
            <xsd:annotation>
                <xsd:documentation>
                  The ReplaceDuplicate value indicates that WFS should
                  not generate a new feature identifier for the feature
                  being inserted into the repositry.  Instead, the WFS
                  should use the identifier encoded if the feature.  
                  If a duplicate exists then the WFS should replace the
                  existing feature instance with the one encoded in the
                  Insert action.
               </xsd:documentation>
            </xsd:annotation>
        </xsd:enumeration>
        <xsd:enumeration value="GenerateNew">
            <xsd:annotation>
                <xsd:documentation>
                  The GenerateNew value indicates that WFS should
                  generate a new unique feature identifier for the
                  feature being inserted into the repositry.
               </xsd:documentation>
            </xsd:annotation>
        </xsd:enumeration>
    </xsd:restriction>
</xsd:simpleType>

• IdentifierGenerationOptionType
• wfs:idgen