<?xml version="1.0" encoding="UTF-8"?>

<StructureDefinition xmlns="http://hl7.org/fhir">
  <id value="Duration"/>
  <text>
    <status value="generated"/>
    <div xmlns="http://www.w3.org/1999/xhtml">
      <table border="0" cellpadding="0" cellspacing="0" style="border: 0px #F0F0F0 solid; font-size: 11px; font-family: verdana; vertical-align: top;">
        <tr style="border: 1px #F0F0F0 solid; font-size: 11px; font-family: verdana; vertical-align: top">
          <th style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; padding-top: 3px; padding-bottom: 3px" class="hierarchy">
            <a href="https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views" title="The logical name of the element">Name</a>
          </th>
          <th style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; padding-top: 3px; padding-bottom: 3px" class="hierarchy">
            <a href="https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views" title="Information about the use of the element">Flags</a>
          </th>
          <th style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; padding-top: 3px; padding-bottom: 3px" class="hierarchy">
            <a href="https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views" title="Minimum and Maximum # of times the element can appear in the instance">Card.</a>
          </th>
          <th style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; padding-top: 3px; padding-bottom: 3px; width: 100px" class="hierarchy">
            <a href="https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views" title="Reference to the type of the element">Type</a>
          </th>
          <th style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; padding-top: 3px; padding-bottom: 3px" class="hierarchy">
            <a href="https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views" title="Additional information about the element">Description &amp; Constraints</a>
            <span style="float: right">
              <a href="https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views" title="Legend for this format">
                <img src="data:image/png;base64,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" alt="doco" style="background-color: inherit"/>
              </a>
            </span>
          </th>
        </tr>
        <tr style="border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: white">
          <td style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAyAAAAACCAYAAACg/LjIAAAAJUlEQVR4Xu3IIQEAAAgDsHd9/w4EQIOamFnaBgAA4MMKAACAKwNp30CqZFfFmwAAAABJRU5ErkJggg==)" class="hierarchy">
            <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAWCAYAAAABxvaqAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3RJTUUH3wYeFzIs1vtcMQAAAB1pVFh0Q29tbWVudAAAAAAAQ3JlYXRlZCB3aXRoIEdJTVBkLmUHAAAAE0lEQVQI12P4//8/AxMDAwNdCABMPwMo2ctnoQAAAABJRU5ErkJggg==" alt="." style="background-color: inherit" class="hierarchy"/>
            <img src="data:image/png;base64,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" alt="." style="background-color: white; background-color: inherit" title="Data Type" class="hierarchy"/> 
            <a href="datatypes-definitions.html#Duration" title="Duration : A length of time.">Duration</a>
          </td>
          <td style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px" class="hierarchy">
            <a style="padding-left: 3px; padding-right: 3px; color: black; null; padding-left: 3px; padding-right: 3px; color: black; null" href="elementdefinition-definitions.html#ElementDefinition.isSummary" title="This element is included in summaries">Σ</a>
            <a style="padding-left: 3px; padding-right: 3px; border: 1px grey solid; font-weight: bold; color: black; background-color: #e6ffe6; padding-left: 3px; padding-right: 3px; border: 1px grey solid; font-weight: bold; color: black; background-color: #e6ffe6" href="versions.html#std-process" title="Standards Status = Normative">N</a>
          </td>
          <td style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px" class="hierarchy"></td>
          <td style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px" class="hierarchy">
            <a href="datatypes.html#Quantity">Quantity</a>
          </td>
          <td style="vertical-align: top; text-align : var(--ig-left,left); background-color: white; border: 0px #F0F0F0 solid; padding:0px 4px 0px 4px" class="hierarchy">A length of time
            <br/>Binding: 
            <a href="valueset-duration-units.html" title="Appropriate units for Duration.">Common UCUM Codes for Duration</a> (
            <a href="terminologies.html#extensible" title="To be conformant, the concept in this element SHALL be from the specified value set if any of the codes within the value set can apply to the concept being communicated.  If the value set does not cover the concept (based on human review), alternate codings (or, data type allowing, text) may be included instead.">Extensible</a>)
            <table class="binding grid">
              <tr>
                <td style="font-size: 11px">
                  <b>Additional Bindings</b>
                </td>
                <td style="font-size: 11px">Purpose</td>
              </tr>
              <tr>
                <td style="font-size: 11px">
                  <a href="valueset-all-time-units.html">All UCUM Expression for Time</a>
                </td>
                <td style="font-size: 11px">
                  <a href="valueset-additional-binding-purpose.html#additional-binding-purpose-maximum" title="A required binding, for use when the binding strength is 'extensible' or 'preferred'">Max Binding</a>
                </td>
              </tr>
            </table>
            <br/>
            <span style="font-style: italic" title="drt-1">+ Rule: There SHALL be a code if there is a value and it SHALL be an expression of time.  If system is present, it SHALL be UCUM.</span>
            <br/>
            <br/>Elements defined in Ancestors: 
            <a href="types.html#Element" title="Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.">id</a>, 
            <a href="types.html#Element" title="May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.">extension</a>, 
            <a href="datatypes.html#Quantity" title="The value of the measured amount. The value includes an implicit precision in the presentation of the value.">value</a>, 
            <a href="datatypes.html#Quantity" title="How the value should be understood and represented - whether the actual value is greater or less than the stated value due to measurement issues; e.g. if the comparator is &quot;&lt;&quot; , then the real value is &lt; stated value.">comparator</a>, 
            <a href="datatypes.html#Quantity" title="A human-readable form of the unit.">unit</a>, 
            <a href="datatypes.html#Quantity" title="The identification of the system that provides the coded form of the unit.">system</a>, 
            <a href="datatypes.html#Quantity" title="A computer processable form of the unit in some unit representation system.">code</a>
          </td>
        </tr>

        <tr>
          <td colspan="5" class="hierarchy">
            <br/>
            <a href="https://build.fhir.org/ig/FHIR/ig-guidance/readingIgs.html#table-views" title="Legend for this format">
              <img src="data:image/png;base64,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" alt="doco" style="background-color: inherit"/> Documentation for this format
            </a>
          </td>
        </tr>
      </table>
    </div>
  </text>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status">
    <valueCode value="normative"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-type-characteristics">
    <valueCode value="has-range"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-type-characteristics">
    <valueCode value="is-continuous"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-type-characteristics">
    <valueCode value="has-units"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-wg">
    <valueCode value="fhir"/>
  </extension>
  <url value="http://hl7.org/fhir/StructureDefinition/Duration"/>
  <version value="6.0.0-ballot4"/>
  <name value="Duration"/>
  <status value="active"/>
  <experimental value="false"/>
  <date value="2026-05-20T06:46:23+00:00"/>
  <publisher value="HL7 International / FHIR Infrastructure"/>
  <contact>
    <telecom>
      <system value="url"/>
      <value value="http://hl7.org/fhir"/>
    </telecom>
  </contact>
  <contact>
    <telecom>
      <system value="url"/>
      <value value="http://www.hl7.org/Special/committees/fiwg"/>
    </telecom>
  </contact>
  <description value="Duration Type: A length of time."/>
  <jurisdiction>
    <coding>
      <system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/>
      <code value="001"/>
      <display value="World"/>
    </coding>
  </jurisdiction>
  <fhirVersion value="6.0.0-ballot4"/>
  <mapping>
    <identity value="rim"/>
    <uri value="http://hl7.org/v3"/>
    <name value="RIM Mapping"/>
  </mapping>
  <mapping>
    <identity value="v2"/>
    <uri value="http://hl7.org/v2"/>
    <name value="HL7 V2 Mapping"/>
  </mapping>
  <kind value="complex-type"/>
  <abstract value="false"/>
  <type value="Duration"/>
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/Quantity"/>
  <derivation value="specialization"/>
  <snapshot>
    <element id="Duration">
      <path value="Duration"/>
      <short value="A length of time"/>
      <definition value="A length of time."/>
      <comment value="The context of use may frequently define what kind of quantity this is and therefore what kind of units can be used. The context of use may also restrict the values for the comparator."/>
      <min value="0"/>
      <max value="*"/>
      <base>
        <path value="Duration"/>
        <min value="0"/>
        <max value="*"/>
      </base>
      <constraint>
        <key value="drt-1"/>
        <severity value="error"/>
        <human value="There SHALL be a code if there is a value and it SHALL be an expression of time.  If system is present, it SHALL be UCUM."/>
        <expression value="code.exists() implies ((system = %ucum) and value.exists())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Duration"/>
      </constraint>
      <constraint>
        <key value="ele-1"/>
        <severity value="error"/>
        <human value="All FHIR elements must have a @value or children"/>
        <expression value="hasValue() or (children().count() &gt; id.count())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/>
      </constraint>
      <constraint>
        <key value="qty-3"/>
        <severity value="error"/>
        <human value="If a code for the unit is present, the system SHALL also be present"/>
        <expression value="code.empty() or system.exists()"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Quantity"/>
      </constraint>
      <constraint>
        <extension url="http://hl7.org/fhir/StructureDefinition/elementdefinition-bestpractice">
          <valueBoolean value="true"/>
        </extension>
        <extension url="http://hl7.org/fhir/StructureDefinition/elementdefinition-bestpractice-explanation">
          <valueMarkdown value="UCUM Codes that contain human readable annotations like {Z-Score} can be misleading. Best Practice is not to use annotations in the UCUM code, and rather to make sure that Quantity.unit is correctly human readable"/>
        </extension>
        <key value="qty-4"/>
        <severity value="warning"/>
        <human value="Processing UCUM codes with annotations ({..}) can be misleading."/>
        <expression value="code.exists() implies code.matches('\\{.*?\\}').not()"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Quantity"/>
      </constraint>
      <isModifier value="false"/>
      <binding>
        <extension url="http://hl7.org/fhir/tools/StructureDefinition/binding-definition">
          <valueMarkdown value="Appropriate units for Duration."/>
        </extension>
        <extension url="http://hl7.org/fhir/StructureDefinition/elementdefinition-bindingName">
          <valueString value="DurationUnits"/>
        </extension>
        <strength value="extensible"/>
        <description value="Appropriate units for Duration."/>
        <valueSet value="http://hl7.org/fhir/ValueSet/duration-units"/>
        <additional>
          <purpose value="maximum"/>
          <valueSet value="http://hl7.org/fhir/ValueSet/all-time-units"/>
        </additional>
      </binding>
      <mapping>
        <identity value="v2"/>
        <map value="SN (see also Range) or CQ"/>
      </mapping>
      <mapping>
        <identity value="rim"/>
        <map value="PQ, IVL&lt;PQ&gt;, MO, CO, depending on the values,PQ, IVL&lt;PQ&gt; depending on the values"/>
      </mapping>
    </element>
    <element id="Duration.id">
      <path value="Duration.id"/>
      <representation value="xmlAttr"/>
      <short value="Unique id for inter-element referencing"/>
      <definition value="Unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces."/>
      <min value="0"/>
      <max value="1"/>
      <base>
        <path value="Element.id"/>
        <min value="0"/>
        <max value="1"/>
      </base>
      <!-- Note: special primitive values have a FHIRPath system type. e.g. this is compiler magic (j) -->
      <type>
        <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type">
          <valueUrl value="string"/>
        </extension>
        <code value="http://hl7.org/fhirpath/System.String"/>
      </type>
      <condition value="ele-1"/>
      <isModifier value="false"/>
      <isSummary value="false"/>
      <mapping>
        <identity value="rim"/>
        <map value="n/a"/>
      </mapping>
    </element>
    <element id="Duration.extension">
      <path value="Duration.extension"/>
      <slicing>
        <discriminator>
          <type value="value"/>
          <path value="url"/>
        </discriminator>
        <description value="Extensions are always sliced by (at least) url"/>
        <rules value="open"/>
      </slicing>
      <short value="Additional content defined by implementations"/>
      <definition value="May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and managable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension."/>
      <comment value="There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions.  The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone."/>
      <alias value="extensions"/>
      <alias value="user content"/>
      <min value="0"/>
      <max value="*"/>
      <base>
        <path value="Element.extension"/>
        <min value="0"/>
        <max value="*"/>
      </base>
      <type>
        <code value="Extension"/>
      </type>
      <constraint>
        <key value="ele-1"/>
        <severity value="error"/>
        <human value="All FHIR elements must have a @value or children"/>
        <expression value="hasValue() or (children().count() &gt; id.count())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/>
      </constraint>
      <isModifier value="false"/>
      <isSummary value="false"/>
      <mapping>
        <identity value="rim"/>
        <map value="n/a"/>
      </mapping>
    </element>
    <element id="Duration.value">
      <path value="Duration.value"/>
      <short value="Numerical value (with implicit precision)"/>
      <definition value="The value of the measured amount. The value includes an implicit precision in the presentation of the value."/>
      <comment value="The implicit precision in the value should always be honored. Monetary values have their own rules for handling precision (refer to standard accounting text books)."/>
      <requirements value="Precision is handled implicitly in almost all cases of measurement."/>
      <min value="0"/>
      <max value="1"/>
      <base>
        <path value="Quantity.value"/>
        <min value="0"/>
        <max value="1"/>
      </base>
      <type>
        <code value="decimal"/>
      </type>
      <constraint>
        <key value="ele-1"/>
        <severity value="error"/>
        <human value="All FHIR elements must have a @value or children"/>
        <expression value="hasValue() or (children().count() &gt; id.count())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/>
      </constraint>
      <isModifier value="false"/>
      <isSummary value="true"/>
      <mapping>
        <identity value="v2"/>
        <map value="SN.2  / CQ - N/A"/>
      </mapping>
      <mapping>
        <identity value="rim"/>
        <map value="PQ.value, CO.value, MO.value, IVL.high or IVL.low depending on the value"/>
      </mapping>
    </element>
    <element id="Duration.comparator">
      <path value="Duration.comparator"/>
      <short value="&lt; | &lt;= | &gt;= | &gt; | ad - how to understand the value"/>
      <definition value="How the value should be understood and represented - whether the actual value is greater or less than the stated value due to measurement issues; e.g. if the comparator is &quot;&lt;&quot; , then the real value is &lt; stated value."/>
      <requirements value="Need a framework for handling measures where the value is &lt;5ug/L or &gt;400mg/L due to the limitations of measuring methodology."/>
      <min value="0"/>
      <max value="1"/>
      <base>
        <path value="Quantity.comparator"/>
        <min value="0"/>
        <max value="1"/>
      </base>
      <type>
        <code value="code"/>
      </type>
      <meaningWhenMissing value="If there is no comparator, then there is no modification of the value"/>
      <constraint>
        <key value="ele-1"/>
        <severity value="error"/>
        <human value="All FHIR elements must have a @value or children"/>
        <expression value="hasValue() or (children().count() &gt; id.count())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/>
      </constraint>
      <isModifier value="true"/>
      <isModifierReason value="This is labeled as &quot;Is Modifier&quot; because the comparator modifies the interpretation of the value significantly. If there is no comparator, then there is no modification of the value"/>
      <isSummary value="true"/>
      <binding>
        <extension url="http://hl7.org/fhir/tools/StructureDefinition/binding-definition">
          <valueMarkdown value="How the Quantity should be understood and represented."/>
        </extension>
        <extension url="http://hl7.org/fhir/StructureDefinition/elementdefinition-bindingName">
          <valueString value="QuantityComparator"/>
        </extension>
        <strength value="required"/>
        <description value="How the Quantity should be understood and represented."/>
        <valueSet value="http://hl7.org/fhir/ValueSet/quantity-comparator|6.0.0-ballot4"/>
      </binding>
      <mapping>
        <identity value="v2"/>
        <map value="SN.1  / CQ.1"/>
      </mapping>
      <mapping>
        <identity value="rim"/>
        <map value="IVL properties"/>
      </mapping>
    </element>
    <element id="Duration.unit">
      <extension url="http://hl7.org/fhir/StructureDefinition/elementdefinition-translatable">
        <valueBoolean value="true"/>
      </extension>
      <path value="Duration.unit"/>
      <short value="Unit representation"/>
      <definition value="A human-readable form of the unit."/>
      <requirements value="There are many representations for units of measure and in many contexts, particular representations are fixed and required. I.e. mcg for micrograms."/>
      <min value="0"/>
      <max value="1"/>
      <base>
        <path value="Quantity.unit"/>
        <min value="0"/>
        <max value="1"/>
      </base>
      <type>
        <code value="string"/>
      </type>
      <constraint>
        <key value="ele-1"/>
        <severity value="error"/>
        <human value="All FHIR elements must have a @value or children"/>
        <expression value="hasValue() or (children().count() &gt; id.count())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/>
      </constraint>
      <isModifier value="false"/>
      <isSummary value="true"/>
      <mapping>
        <identity value="v2"/>
        <map value="(see OBX.6 etc.) / CQ.2"/>
      </mapping>
      <mapping>
        <identity value="rim"/>
        <map value="PQ.unit"/>
      </mapping>
    </element>
    <element id="Duration.system">
      <path value="Duration.system"/>
      <short value="System that defines coded unit form"/>
      <definition value="The identification of the system that provides the coded form of the unit."/>
      <requirements value="Need to know the system that defines the coded form of the unit."/>
      <min value="0"/>
      <max value="1"/>
      <base>
        <path value="Quantity.system"/>
        <min value="0"/>
        <max value="1"/>
      </base>
      <type>
        <code value="uri"/>
      </type>
      <condition value="qty-3"/>
      <constraint>
        <key value="ele-1"/>
        <severity value="error"/>
        <human value="All FHIR elements must have a @value or children"/>
        <expression value="hasValue() or (children().count() &gt; id.count())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/>
      </constraint>
      <isModifier value="false"/>
      <isSummary value="true"/>
      <mapping>
        <identity value="v2"/>
        <map value="(see OBX.6 etc.) / CQ.2"/>
      </mapping>
      <mapping>
        <identity value="rim"/>
        <map value="CO.codeSystem, PQ.translation.codeSystem"/>
      </mapping>
    </element>
    <element id="Duration.code">
      <extension url="http://hl7.org/fhir/tools/StructureDefinition/no-binding">
        <valueBoolean value="true"/>
      </extension>
      <path value="Duration.code"/>
      <short value="Coded form of the unit"/>
      <definition value="A computer processable form of the unit in some unit representation system."/>
      <comment value="The preferred system is UCUM, but SNOMED CT can also be used (for customary units) or ISO 4217 for currency.  The context of use may additionally require a code from a particular system."/>
      <requirements value="Need a computable form of the unit that is fixed across all forms. UCUM provides this for quantities, but SNOMED CT provides many units of interest."/>
      <min value="0"/>
      <max value="1"/>
      <base>
        <path value="Quantity.code"/>
        <min value="0"/>
        <max value="1"/>
      </base>
      <type>
        <code value="code"/>
      </type>
      <condition value="qty-3"/>
      <constraint>
        <key value="ele-1"/>
        <severity value="error"/>
        <human value="All FHIR elements must have a @value or children"/>
        <expression value="hasValue() or (children().count() &gt; id.count())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/>
      </constraint>
      <isModifier value="false"/>
      <isSummary value="true"/>
      <mapping>
        <identity value="v2"/>
        <map value="(see OBX.6 etc.) / CQ.2"/>
      </mapping>
      <mapping>
        <identity value="rim"/>
        <map value="PQ.code, MO.currency, PQ.translation.code"/>
      </mapping>
    </element>
  </snapshot>
  <differential>
    <element id="Duration">
      <path value="Duration"/>
      <short value="A length of time"/>
      <definition value="A length of time."/>
      <min value="0"/>
      <max value="*"/>
      <constraint>
        <key value="drt-1"/>
        <severity value="error"/>
        <human value="There SHALL be a code if there is a value and it SHALL be an expression of time.  If system is present, it SHALL be UCUM."/>
        <expression value="code.exists() implies ((system = %ucum) and value.exists())"/>
        <source value="http://hl7.org/fhir/StructureDefinition/Duration"/>
      </constraint>
      <binding>
        <extension url="http://hl7.org/fhir/tools/StructureDefinition/binding-definition">
          <valueMarkdown value="Appropriate units for Duration."/>
        </extension>
        <extension url="http://hl7.org/fhir/StructureDefinition/elementdefinition-bindingName">
          <valueString value="DurationUnits"/>
        </extension>
        <strength value="extensible"/>
        <description value="Appropriate units for Duration."/>
        <valueSet value="http://hl7.org/fhir/ValueSet/duration-units"/>
        <additional>
          <purpose value="maximum"/>
          <valueSet value="http://hl7.org/fhir/ValueSet/all-time-units"/>
        </additional>
      </binding>
      <mapping>
        <identity value="rim"/>
        <map value="PQ, IVL&lt;PQ&gt; depending on the values"/>
      </mapping>
    </element>
  </differential>
</StructureDefinition>