How to make this work? for example:
<xs:element name="name"
type="xs:string"
substitutionGroup="firstname"/>
for this code bellow...
<xs:complexType name="basic">
<xs:sequence>
<xs:element name="firstname" type="xs:string" />
<xs:element name="lastname" type="xs:string" />
</xs:sequence>
</xs:complexType>