<xs:simpleType name="taskConstraintType">
  <xs:annotation>
    <xs:documentation>The time constraint type (can be "as soon as possible", "as late as possible", "must start on...", "must finish on...", "start no earlier than...", "start no later than...", "finish no earlier than...", "finish no later than")</xs:documentation>
  </xs:annotation>
  <xs:restriction base="xs:NMTOKEN">
    <xs:enumeration value="as_soon_as_possible"/>
    <xs:enumeration value="as_late_as_possible"/>
    <xs:enumeration value="must_start_on"/>
    <xs:enumeration value="must_finish_on"/>
    <xs:enumeration value="start_no_earlier_than"/>
    <xs:enumeration value="start_no_later_than"/>
    <xs:enumeration value="finish_no_earlier_than"/>
    <xs:enumeration value="finish_no_later_than"/>
  </xs:restriction>
</xs:simpleType>