<xs:schema xmlns:xs=“www.w3.org/2001/XMLSchema”>
<xs:element name="odd-page" type="xs:string"/> <xs:element name="even-page" type="xs:string"/> <xs:element name="book"> <xs:complexType> <xs:sequence> <xs:sequence minOccurs="0" maxOccurs="unbounded"> <xs:element ref="odd-page"/> <xs:element ref="even-page"/> </xs:sequence> <xs:element ref="odd-page" minOccurs="0"/> </xs:sequence> </xs:complexType> </xs:element>
</xs:schema>