<xs:schema xmlns:xs=“www.w3.org/2001/XMLSchema” xmlns=“FOO” targetNamespace=“FOO”>
<xs:element name="foo"> <xs:complexType> <xs:complexContent> <xs:restriction base="typeA"> <xs:attribute name="barA" type="xs:string" use="optional"/> </xs:restriction> </xs:complexContent> </xs:complexType> </xs:element> <xs:complexType name="typeA"> <xs:attribute name="barA" type="xs:string" use="required"/> </xs:complexType>
</xs:schema>