<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:my_ns="http://my/ns" 
           targetNamespace="http://my/ns"
           elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="main_elt">
    <xs:complexType>
        <xs:sequence>
            <xs:element name="attr" type="xs:string"/>
        </xs:sequence>
    </xs:complexType>
</xs:element>
</xs:schema>
