Example for restriction

  <complexType name="Name">
    <sequence>
      <element name="Surname"   type="string"/>
      <element name="FirstName" type="string"
         minOccurs="1" maxOccurs="unbounded"/>
    </sequence>
  </element>
  <complexType name="SimpleName">
    <complexContent>
      <restriction base="Name">
        <sequence>
          <element name="Surname"   type="string"/>
          <element name="FirstName" type="string"
             minOccurs="1" maxOccurs="1"/>
        </sequence>
      </restriction>
    </complexContent>
  </complexType>

Ie, only one first name is allowed>