A complex type can be extended to add some number of additional element children.

The 'extension' element child contains some number of content particles (e.g. element, sequence, etc.) before the attributes.

The content of the element is the base type's content plus the

Example:

<xs:complexType name="Person">
   <xs:sequence>
   <xs:element ref="my:name"/>
   <xs:element ref="my:major"/>
   </xs:sequence>
</xs:complexType>

<xs:complexType name="LocatedPerson">
   <xs:complexContent>
      <xs:extension base="my:Person">
         <xs:element ref="my:address"/>
      </xs:extension>
   </xs:complexContent>
</xs:complexType>