The XML Schema elves cooked this up over night while you slept:

  <xs:element name="order">
     <xs:complexType>
        <xs:sequence>
        <xs:element ref="my:pizza" maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute name="taken-on" type="xs:dateTime" use="required"/>
        <xs:attribute name="on-its-way" type="xs:boolean"/>
        <xs:attribute name="delivered-on" type="xs:dateTime"/>
     </xs:complexType>
  </xs:element>

But now we need to declare my:pizza...