Types date, time and dateTime.

Hi !

I´m learning XML Schema and I´ll like suggest a normalization of the types 
date, time and their derivations. I believe this facilit the manipulation 
the data from an application.
E.g.
<xs:element name="testDate" type="xs:date>
     <xs:complexType>
         <xs:sequence>
             <xs:element name="testYear" type="xs:year"/>
             <xs:element name="testMonth" type="xs:month"/>
             <xs:element name="testDay" type="xs:day"/>
         </xs:sequence>
     </xs:complexType>
</xs:element>

My doubt is what element the restriction must be made: In the complexType 
(date) or in the sympleType (year, month and day).

Regards for your attention,

Roberto Hideki Tatemoto
São Paulo Brazil