<simpleType name="RelationTypeEnumType">
  <restriction base="string">
    <enumeration value="shaft t-z">
      <annotation>
        <documentation>The shaft load-transfer relation: mobilized shaft shear stress versus relative shaft and soil displacement.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="tip q-z">
      <annotation>
        <documentation>The tip (base) load-transfer relation: mobilized unit tip resistance versus tip displacement.</documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>