<?xml version=“1.0”?> <xs:schema xmlns:xs=“www.w3.org/2001/XMLSchema”>
<xs:complexType name="Item" abstract="true"> <xs:sequence minOccurs="1" maxOccurs="unbounded"> <xs:element name="Name" type="xs:string"/> </xs:sequence> </xs:complexType> <xs:complexType name="ItemWithNumber"> <xs:complexContent> <xs:extension base="Item"> <xs:sequence> <xs:element name="Number" type="xs:nonNegativeInteger"/> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> <xs:element name="ItemsList"> <xs:complexType> <xs:sequence> <xs:element name="Item" type="Item" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> </xs:element>
</xs:schema>