<xsd:complexType name="DocumentReferenceBaseType" abstract="true"> <xsd:sequence> <xsd:group ref="DocumentIDsGroup" /> <xsd:element ref="DocumentDateTime" minOccurs="0" /> <xsd:group ref="FreeFormTextGroup" /> <xsd:element ref="StatusCode" minOccurs="0" /> </xsd:sequence> </xsd:complexType>