<xsd:complexType name="NA"> <xsd:sequence> <xsd:element ref="NA.1" minOccurs="0" maxOccurs="1" /> <xsd:element ref="NA.2" minOccurs="0" maxOccurs="1" /> <xsd:element ref="NA.3" minOccurs="0" maxOccurs="1" /> <xsd:element ref="NA.4" minOccurs="0" maxOccurs="1" /> </xsd:sequence> </xsd:complexType>