customer

<xs:element name="customer">
  <xs:complexType>
    <xs:sequence>
      <xs:element ref="contact"/>
      <xs:element ref="id" minOccurs="0" maxOccurs="unbounded"/>
      <xs:element ref="timeframe" minOccurs="0"/>
      <xs:element ref="comments" minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>
</xs:element>