Release 5 Preview #2

Period.profile.xml

Modeling and Methodology Work GroupMaturity Level: N/AStandards Status: Informative

Raw XML (canonical form + also see XML Format Specification)

StructureDefinition for Period

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

<StructureDefinition xmlns="http://hl7.org/fhir">
  <id value="Period"/> 
  <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 class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="formats.html#table" title="The logical name of the element">Name</a> 
          </th> 
          <th class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="formats.html#table" title="Information about the use of the element">Flags</a> 
          </th> 
          <th class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="formats.html#table" title="Minimum and Maximum # of times the the element can appear in the instance">Card.</a> 
          </th> 
          <th class="hierarchy" style="width: 100px">
            <a href="formats.html#table" title="Reference to the type of the element">Type</a> 
          </th> 
          <th class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="formats.html#table" title="Additional information about the element">Description &amp; Constraints</a> 
            <span style="float: right">
              <a href="formats.html#table" title="Legend for this format">
                <img alt="doco" src="help16.png" style="background-color: inherit"/> 
              </a> 
            </span> 
          </th> 
        </tr> 
        <tr style="border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: white;">
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(data:image/png;base64,iVBORw0KGg
          oAAAANSUhEUgAAAyAAAAACCAYAAACg/LjIAAAAI0lEQVR42u3QIQEAAAACIL/6/4MvTAQOkLYBAAB4kAAAANwMad9AqkRjgNAAAAA
          ASUVORK5CYII=)">
            <img alt="." class="hierarchy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAWCAYAAAABxvaqAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3
            RJTUUH3wYeFzIs1vtcMQAAAB1pVFh0Q29tbWVudAAAAAAAQ3JlYXRlZCB3aXRoIEdJTVBkLmUHAAAAE0lEQVQI12P4//8/AxMDAwN
            dCABMPwMo2ctnoQAAAABJRU5ErkJggg==" style="background-color: inherit"/> 
            <img alt="." class="hierarchy" src="data:image/png;base64,R0lGODlhEAAQAPQfAOvGUf7ztuvPMf/78/fkl/Pbg+u8Rvjqteu2Pf3zxPz36Pz0z+vTmPzurPvuw/
            npofbjquvNefHVduuyN+uuMu3Oafbgjfnqvf/3zv/3xevPi+vRjP/20/bmsP///wD/ACH5BAEKAB8ALAAAAAAQABAAAAVl4CeOZGm
            e5qCqqDg8jyVJaz1876DsmAQAgqDgltspMEhMJoMZ4iy6I1AooFCIv+wKybziALVAoAEjYLwDgGIpJhMslgxaLR4/3rMAWoBp32V5
            exg8Shl1ckRUQVaMVkQ2kCstKCEAOw==" style="background-color: white; background-color: inherit" title="Element"/>  
            <a href="datatypes-definitions.html#Period" title="Period : A time period defined by a start and end date and optionally time.">Period</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="elementdefinition-definitions.html#ElementDefinition.isSummary" style="padding-left: 3px; padding-right: 3px; color: black; null" title="This element is included in summaries">Σ</a> 
            <a href="versions.html#std-process" style="padding-left: 3px; padding-right: 3px; border: 1px grey solid; font-weight: bold; color:
             black; background-color: #e6ffe6" title="Standards Status = Normative">N</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px"/> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="types.html#Element">Element</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">Time range defined by start and end date/time
            <br/>  
            <span style="font-style: italic" title="per-1">+ Rule: If present, start SHALL have a lower value than end</span> 
            <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 manageable, 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> 
          </td> 
        </tr> 

        <tr style="border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: #F7F7F7;">
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0
           solid; padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(data:image/png;base64,iVB
          ORw0KGgoAAAANSUhEUgAAAyAAAAACCAYAAACg/LjIAAAAL0lEQVR42u3XsQ0AQAgCQHdl/xn8jxvYWB3JlTR0VJLa+OltBwAAYP6E
          EQAAgCsPVYVAgIJrA/sAAAAASUVORK5CYII=)">
            <img alt="." class="hierarchy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAWCAYAAAABxvaqAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3
            RJTUUH3wYeFzIs1vtcMQAAAB1pVFh0Q29tbWVudAAAAAAAQ3JlYXRlZCB3aXRoIEdJTVBkLmUHAAAAE0lEQVQI12P4//8/AxMDAwN
            dCABMPwMo2ctnoQAAAABJRU5ErkJggg==" style="background-color: inherit"/> 
            <img alt="." class="hierarchy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAWCAYAAADJqhx8AAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3
            RJTUUH3wYeFzI3XJ6V3QAAAB1pVFh0Q29tbWVudAAAAAAAQ3JlYXRlZCB3aXRoIEdJTVBkLmUHAAAANklEQVQ4y+2RsQ0AIAzDav7
            /2VzQwoCY4iWbZSmo1QGoUgNMghvWaIejPQW/CrrNCylIwcOCDYfLNRcNer4SAAAAAElFTkSuQmCC" style="background-color: inherit"/> 
            <img alt="." class="hierarchy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAACXBIWXMAAAsTAAALEwEAmpwYAAAARk
            lEQVQ4y2P8//8/AyWAhYFCMAgMuHjx4n+KXaCv+I0szW8WpCG8kFO1lGFKW/SIjAUYgxz/MzAwMDC+nqhDUTQyjuYFBgCNmhP4OvT
            RgwAAAABJRU5ErkJggg==" style="background-color: #F7F7F7; background-color: inherit" title="Primitive Data Type"/>  
            <a href="datatypes-definitions.html#Period.start" title="Period.start : The start of the period. The boundary is inclusive.">start</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0
           solid; padding:0px 4px 0px 4px">
            <a href="elementdefinition-definitions.html#ElementDefinition.isSummary" style="padding-left: 3px; padding-right: 3px; color: black; null" title="This element is included in summaries">Σ</a> 
            <a href="conformance-rules.html#constraints" style="padding-left: 3px; padding-right: 3px; color: black; null" title="This element has or is affected by some invariants">I</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0
           solid; padding:0px 4px 0px 4px">0..1</td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0
           solid; padding:0px 4px 0px 4px">
            <a href="datatypes.html#dateTime">dateTime</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: #F7F7F7; border: 0px #F0F0F0
           solid; padding:0px 4px 0px 4px">Starting time with inclusive boundary</td> 
        </tr> 

        <tr style="border: 0px #F0F0F0 solid; padding:0px; vertical-align: top; background-color: white;">
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px; white-space: nowrap; background-image: url(data:image/png;base64,iVBORw0KGg
          oAAAANSUhEUgAAAyAAAAACCAYAAACg/LjIAAAAI0lEQVR42u3QIQEAAAACIL/6/4MvTAQOkLYBAAB4kAAAANwMad9AqkRjgNAAAAA
          ASUVORK5CYII=)">
            <img alt="." class="hierarchy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAWCAYAAAABxvaqAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3
            RJTUUH3wYeFzIs1vtcMQAAAB1pVFh0Q29tbWVudAAAAAAAQ3JlYXRlZCB3aXRoIEdJTVBkLmUHAAAAE0lEQVQI12P4//8/AxMDAwN
            dCABMPwMo2ctnoQAAAABJRU5ErkJggg==" style="background-color: inherit"/> 
            <img alt="." class="hierarchy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAWCAYAAADJqhx8AAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3
            RJTUUH3wYeFzME+lXFigAAAB1pVFh0Q29tbWVudAAAAAAAQ3JlYXRlZCB3aXRoIEdJTVBkLmUHAAAANklEQVQ4y+3OsRUAIAjEUOL
            +O8cJABttJM11/x1qZAGqRBEVcNIqdWj1efDqQbb3HwwwwEfABmQUHSPM9dtDAAAAAElFTkSuQmCC" style="background-color: inherit"/> 
            <img alt="." class="hierarchy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAACXBIWXMAAAsTAAALEwEAmpwYAAAARk
            lEQVQ4y2P8//8/AyWAhYFCMAgMuHjx4n+KXaCv+I0szW8WpCG8kFO1lGFKW/SIjAUYgxz/MzAwMDC+nqhDUTQyjuYFBgCNmhP4OvT
            RgwAAAABJRU5ErkJggg==" style="background-color: white; background-color: inherit" title="Primitive Data Type"/>  
            <a href="datatypes-definitions.html#Period.end" title="Period.end : The end of the period. If the end of the period is missing, it means no end
             was known or planned at the time the instance was created. The start may be in the past,
             and the end date in the future, which means that period is expected/planned to end at
             that time.">end</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="elementdefinition-definitions.html#ElementDefinition.isSummary" style="padding-left: 3px; padding-right: 3px; color: black; null" title="This element is included in summaries">Σ</a> 
            <a href="conformance-rules.html#constraints" style="padding-left: 3px; padding-right: 3px; color: black; null" title="This element has or is affected by some invariants">I</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">0..1</td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">
            <a href="datatypes.html#dateTime">dateTime</a> 
          </td> 
          <td class="hierarchy" style="vertical-align: top; text-align : left; background-color: white; border: 0px #F0F0F0 solid;
           padding:0px 4px 0px 4px">End time with inclusive boundary, if not ongoing</td> 
        </tr> 

        <tr> 
          <td class="hierarchy" colspan="5">
            <br/>  
            <a href="formats.html#table" title="Legend for this format">
              <img alt="doco" src="help16.png" 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-normative-version">
    <valueCode value="4.0.0"/> 
  </extension> 
  <url value="http://hl7.org/fhir/StructureDefinition/Period"/> 
  <version value="4.4.0"/> 
  <name value="Period"/> 
  <status value="active"/> 
  <date value="2020-06-04T23:31:40+00:00"/> 
  <publisher value="HL7 FHIR Standard"/> 
  <contact> 
    <telecom> 
      <system value="url"/> 
      <value value="http://hl7.org/fhir"/> 
    </telecom> 
  </contact> 
  <description value="Base StructureDefinition for Period Type: A time period defined by a start and end date
   and optionally time."/> 
  <fhirVersion value="4.4.0"/> 
  <mapping> 
    <identity value="v2"/> 
    <uri value="http://hl7.org/v2"/> 
    <name value="HL7 v2 Mapping"/> 
  </mapping> 
  <mapping> 
    <identity value="rim"/> 
    <uri value="http://hl7.org/v3"/> 
    <name value="RIM Mapping"/> 
  </mapping> 
  <kind value="complex-type"/> 
  <abstract value="false"/> 
  <type value="Period"/> 
  <baseDefinition value="http://hl7.org/fhir/StructureDefinition/DataType"/> 
  <derivation value="specialization"/> 
  <snapshot> 
    <element id="Period">
      <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status">
        <valueCode value="normative"/> 
      </extension> 
      <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-normative-version">
        <valueCode value="4.0.0"/> 
      </extension> 
      <path value="Period"/> 
      <short value="Time range defined by start and end date/time"/> 
      <definition value="A time period defined by a start and end date and optionally time."/> 
      <comment value="A Period specifies a range of time; the context of use will specify whether the entire
       range applies (e.g. &quot;the patient was an inpatient of the hospital for this time range&quot;)
       or one value from the range applies (e.g. &quot;give to the patient between these two
       times&quot;).

Period is not used for a duration (a measure of elapsed time). See [Duration](datatypes.html#Duratio
      n)."/> 
      <min value="0"/> 
      <max value="*"/> 
      <base> 
        <path value="Period"/> 
        <min value="0"/> 
        <max value="*"/> 
      </base> 
      <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())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="per-1"/> 
        <severity value="error"/> 
        <human value="If present, start SHALL have a lower value than end"/> 
        <expression value="start.hasValue().not() or end.hasValue().not() or (start &lt;= end)"/> 
        <xpath value="not(exists(f:start/@value)) or not(exists(f:end/@value)) or (xs:dateTime(f:start/@value)
         &lt;= xs:dateTime(f:end/@value))"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Period"/> 
      </constraint> 
      <isModifier value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
      <mapping> 
        <identity value="v2"/> 
        <map value="DR"/> 
      </mapping> 
      <mapping> 
        <identity value="rim"/> 
        <map value="IVL&lt;TS&gt;[lowClosed=&quot;true&quot; and highClosed=&quot;true&quot;] or URG&lt;TS&gt;[lowClosed
        =&quot;true&quot; and highClosed=&quot;true&quot;]"/> 
      </mapping> 
    </element> 
    <element id="Period.id">
      <path value="Period.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">
          <valueUri value="string"/> 
        </extension> 
        <code value="http://hl7.org/fhirpath/System.String"/> 
      </type> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Period.extension">
      <path value="Period.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 manageable, 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())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <constraint> 
        <key value="ext-1"/> 
        <severity value="error"/> 
        <human value="Must have either extensions or value[x], not both"/> 
        <expression value="extension.exists() != value.exists()"/> 
        <xpath value="exists(f:extension)!=exists(f:*[starts-with(local-name(.), &quot;value&quot;)])"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Extension"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="false"/> 
      <mapping> 
        <identity value="rim"/> 
        <map value="n/a"/> 
      </mapping> 
    </element> 
    <element id="Period.start">
      <path value="Period.start"/> 
      <short value="Starting time with inclusive boundary"/> 
      <definition value="The start of the period. The boundary is inclusive."/> 
      <comment value="If the low element is missing, the meaning is that the low boundary is not known."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Period.start"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <code value="dateTime"/> 
      </type> 
      <condition value="per-1"/> 
      <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())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="true"/> 
      <mapping> 
        <identity value="v2"/> 
        <map value="DR.1"/> 
      </mapping> 
      <mapping> 
        <identity value="rim"/> 
        <map value="./low"/> 
      </mapping> 
    </element> 
    <element id="Period.end">
      <path value="Period.end"/> 
      <short value="End time with inclusive boundary, if not ongoing"/> 
      <definition value="The end of the period. If the end of the period is missing, it means no end was known
       or planned at the time the instance was created. The start may be in the past, and the
       end date in the future, which means that period is expected/planned to end at that time."/> 
      <comment value="The high value includes any matching date/time. i.e. 2012-02-03T10:00:00 is in a period
       that has an end value of 2012-02-03."/> 
      <min value="0"/> 
      <max value="1"/> 
      <base> 
        <path value="Period.end"/> 
        <min value="0"/> 
        <max value="1"/> 
      </base> 
      <type> 
        <code value="dateTime"/> 
      </type> 
      <meaningWhenMissing value="If the end of the period is missing, it means that the period is ongoing"/> 
      <condition value="per-1"/> 
      <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())"/> 
        <xpath value="@value|f:*|h:div"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Element"/> 
      </constraint> 
      <isModifier value="false"/> 
      <isSummary value="true"/> 
      <mapping> 
        <identity value="v2"/> 
        <map value="DR.2"/> 
      </mapping> 
      <mapping> 
        <identity value="rim"/> 
        <map value="./high"/> 
      </mapping> 
    </element> 
  </snapshot> 
  <differential> 
    <element id="Period">
      <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status">
        <valueCode value="normative"/> 
      </extension> 
      <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-normative-version">
        <valueCode value="4.0.0"/> 
      </extension> 
      <path value="Period"/> 
      <short value="Time range defined by start and end date/time"/> 
      <definition value="A time period defined by a start and end date and optionally time."/> 
      <comment value="A Period specifies a range of time; the context of use will specify whether the entire
       range applies (e.g. &quot;the patient was an inpatient of the hospital for this time range&quot;)
       or one value from the range applies (e.g. &quot;give to the patient between these two
       times&quot;).

Period is not used for a duration (a measure of elapsed time). See [Duration](datatypes.html#Duratio
      n)."/> 
      <min value="0"/> 
      <max value="*"/> 
      <constraint> 
        <key value="per-1"/> 
        <severity value="error"/> 
        <human value="If present, start SHALL have a lower value than end"/> 
        <expression value="start.hasValue().not() or end.hasValue().not() or (start &lt;= end)"/> 
        <xpath value="not(exists(f:start/@value)) or not(exists(f:end/@value)) or (xs:dateTime(f:start/@value)
         &lt;= xs:dateTime(f:end/@value))"/> 
        <source value="http://hl7.org/fhir/StructureDefinition/Period"/> 
      </constraint> 
      <mapping> 
        <identity value="v2"/> 
        <map value="DR"/> 
      </mapping> 
      <mapping> 
        <identity value="rim"/> 
        <map value="IVL&lt;TS&gt;[lowClosed=&quot;true&quot; and highClosed=&quot;true&quot;] or URG&lt;TS&gt;[lowClosed
        =&quot;true&quot; and highClosed=&quot;true&quot;]"/> 
      </mapping> 
    </element> 
    <element id="Period.start">
      <path value="Period.start"/> 
      <short value="Starting time with inclusive boundary"/> 
      <definition value="The start of the period. The boundary is inclusive."/> 
      <comment value="If the low element is missing, the meaning is that the low boundary is not known."/> 
      <min value="0"/> 
      <max value="1"/> 
      <type> 
        <code value="dateTime"/> 
      </type> 
      <condition value="per-1"/> 
      <isSummary value="true"/> 
      <mapping> 
        <identity value="v2"/> 
        <map value="DR.1"/> 
      </mapping> 
      <mapping> 
        <identity value="rim"/> 
        <map value="./low"/> 
      </mapping> 
    </element> 
    <element id="Period.end">
      <path value="Period.end"/> 
      <short value="End time with inclusive boundary, if not ongoing"/> 
      <definition value="The end of the period. If the end of the period is missing, it means no end was known
       or planned at the time the instance was created. The start may be in the past, and the
       end date in the future, which means that period is expected/planned to end at that time."/> 
      <comment value="The high value includes any matching date/time. i.e. 2012-02-03T10:00:00 is in a period
       that has an end value of 2012-02-03."/> 
      <min value="0"/> 
      <max value="1"/> 
      <type> 
        <code value="dateTime"/> 
      </type> 
      <meaningWhenMissing value="If the end of the period is missing, it means that the period is ongoing"/> 
      <condition value="per-1"/> 
      <isSummary value="true"/> 
      <mapping> 
        <identity value="v2"/> 
        <map value="DR.2"/> 
      </mapping> 
      <mapping> 
        <identity value="rim"/> 
        <map value="./high"/> 
      </mapping> 
    </element> 
  </differential> 
</StructureDefinition> 

Usage note: every effort has been made to ensure that the examples are correct and useful, but they are not a normative part of the specification.