Attempt at demonstrating OrderSet chemotherapy regimen timing using as few extensions as possible

KDN5.xml

<OrderSet>
  <moduleMetadata>
    <identifier>
      <system value="http://nccn.org/ordertemplates" />
      <value value="KDN5" />
    </identifier>
  </module>

  <!-- Here we only have one course (which repeats for 6 21-day cycles), but we could have multiple courses -->
  <action>
    <title value="Course 1: Gemcitabine and Carboplatin"/>
    <actionIdentifier><value value="#course-1"/></actionIdentifier>

    <!-- Here's the only extension: cycle, which just uses regular Timing -->
    <extension url="http://example.com/fhir/cycle">
      <timing>
        <repeat>
          <count value="6" />
          <period value="21" />
          <periodUnit value="d" />
        </repeat>
      </timing>
    </extension>

    <!-- Cycle sub-actions -->
    <action>
      <!-- Gemcitabine sub-action -->
      <action>
        <title value="Gemcitabine 1250 mg/m2 IV over 30 minutes on Days 1 and 8"/>
        <resource>
          <reference value="#gemcitabine-order"/>
        </resource>
        <relatedAction>
          <!-- The offset is relative to the course, but implicitly, it's relative to each cycle -->
          <!-- Could also have a special actionIdentifier that represents "each cycle", e.g. "#course-1-cycle" -->
          <actionIdentifier><value value="#course-1"/></actionIdentifier>
          <anchor value="start"/>
        </relatedAction>
      </action>

      <!-- Carboplatin sub-action. NOTE: I changed this to day 2 to demonstrate offseting -->
      <action>
        <title value="Carboplatin AUC 5 IV over 30 minutes on Day 2"/> 
        <resource>
          <reference value="#carboplatin-order"/>
        </resource>
        <relatedAction>
          <actionIdentifier><value value="#course-1"/></actionIdentifier>
          <anchor value="start"/>
          <offset>
            <value value="1"/>
            <unit value="d"/>
          </offset>
        </relatedAction>
      </action>
    </action>
  </action>

  <!-- Contained MedicationOrders referenced in the sub-actions -->
  <contained>
    <!-- Gemcitabine has a repeat; happens twice, separated by a week -->
    <MedicationOrder>
      <id value="gemcitabine-order"/>
      <dosageInstruction>
        <text value="1250 mg/m² IV over 30 minutes on days 1 and 8" />
        <doseQuantity>
          <value value="1250" />
          <unit value="mg/m²" />
        </doseQuantity>
        <route>
          <text value="IV" />
        </route>
        <timing>
          <repeat>
            <count value="2"/>
            <period value="7"/>
            <periodUnit value="d"/>
            <duration value="30" />
            <durationUnit value="min" />
          </repeat>
        </timing>
      </dosageInstruction>
    </MedicationOrder>

    <!-- Carboplatin has no repeat; happens only once -->
    <MedicationOrder>
      <id value="carboplatin-order"/>
      <dosageInstruction>
        <text value="CARBOplatin AUC 5 IV over 30 minutes on Day 2" />
        <doseQuantity>
          <value value="5" />
          <unit value="AUC" />
        </doseQuantity>
        <route>
          <text value="IV" />
        </route>
        <timing>
          <repeat>
            <count value="1"/>
            <duration value="30" />
            <durationUnit value="min" />
          </repeat>
        </timing>
      </dosageInstruction>
    </MedicationOrder>
  </contained>
</OrderSet>