(...)
<xs:complexType name="ExportType">
<xs:sequence>
  <xs:element name="Statements" type="statementstype:StatementsType" minOccurs="0" maxOccurs="1"/>
  <xs:element name="Operation" type="operationtype:OperationType" minOccurs="1" maxOccurs="1"/>
  <xs:element name="SelectedLanguageDescriptions" type="languagedescriptionstype:LanguageDescriptionsType" minOccurs="0" maxOccurs="1"/>
</xs:sequence>
</xs:complexType>
(...)
<xs:complexType name="OperationType">
<xs:choice>
  <xs:element name="Extract" type="extracttype:ExtractType"/>
  <xs:element name="Retrieve" type="retrievetype:RetrieveType"/>
  <xs:element name="SynchronisationExtract" type="synchronisationextracttype:SynchronisationExtractType"/>
</xs:choice>
</xs:complexType>
(...)