Yes/No/Don't know, for capturing a common answer set in questionnaires (id = "yesnodontknow")

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

<ValueSet xmlns="http://hl7.org/fhir">
  <id value="yesnodontknow"/> 
  <text> 
    <status value="generated"/> 
    <div xmlns="http://www.w3.org/1999/xhtml">
      <p> This value set expansion contains 3 concepts.</p> 
      <table class="codes">
        <tr> 
          <td style="white-space:nowrap">
            <b> Code</b> 
          </td> 
          <td> 
            <b> System</b> 
          </td> 
          <td> 
            <b> Display</b> 
          </td> 
          <td> 
            <b> Definition</b> 
          </td> 
        </tr> 
        <tr> 
          <td style="white-space:nowrap">
            <a name="http---terminology.hl7.org-CodeSystem-v2-0532-Y"> </a>   
            <a href="http://terminology.hl7.org/5.5.0/CodeSystem-v2-0532.html#v2-0532-Y">Y</a> 
          </td> 
          <td> http://terminology.hl7.org/CodeSystem/v2-0532</td> 
          <td> Yes</td> 
          <td> 
            <div> 
              <p> Yes</p> 

            </div> 
          </td> 
        </tr> 
        <tr> 
          <td style="white-space:nowrap">
            <a name="http---terminology.hl7.org-CodeSystem-v2-0532-N"> </a>   
            <a href="http://terminology.hl7.org/5.5.0/CodeSystem-v2-0532.html#v2-0532-N">N</a> 
          </td> 
          <td> http://terminology.hl7.org/CodeSystem/v2-0532</td> 
          <td> No</td> 
          <td> 
            <div> 
              <p> No</p> 

            </div> 
          </td> 
        </tr> 
        <tr> 
          <td style="white-space:nowrap">
            <a name="http---terminology.hl7.org-CodeSystem-data-absent-reason-asked-unknown"> </a>   
            <a href="http://terminology.hl7.org/5.5.0/CodeSystem-data-absent-reason.html#data-absent-reason-asked-
            unknown">asked-unknown</a> 
          </td> 
          <td> http://terminology.hl7.org/CodeSystem/data-absent-reason</td> 
          <td> Don't know</td> 
          <td> 
            <div> 
              <p> The source was asked but does not know the value.</p> 

            </div> 
          </td> 
        </tr> 
      </table> 
    </div> 
  </text> 
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-wg">
    <valueCode value="vocab"/> 
  </extension> 
  <url value="http://hl7.org/fhir/ValueSet/yesnodontknow"/> 
  <identifier> 
    <system value="urn:ietf:rfc:3986"/> 
    <value value="urn:oid:2.16.840.1.113883.4.642.3.3149"/> 
  </identifier> 
  <version value="6.0.0-cibuild"/> 
  <name value="YesNoDontKnow"/> 
  <title value="Yes/No/Don't Know"/> 
  <status value="draft"/> 
  <experimental value="true"/> 
  <publisher value="HL7 International / Terminology Infrastructure"/> 
  <contact> 
    <telecom> 
      <system value="url"/> 
      <value value="http://www.hl7.org/Special/committees/Vocab"/> 
    </telecom> 
  </contact> 
  <contact> 
    <telecom> 
      <system value="url"/> 
      <value value="http://www.hl7.org/Special/committees/Vocab/index.cfm"/> 
    </telecom> 
  </contact> 
  <description value="For Capturing simple yes-no-don't know answers"/> 
  <compose> 
    <include> 
      <valueSet value="http://terminology.hl7.org/ValueSet/v2-0136"/> 
    </include> 
    <include> 
      <system value="http://terminology.hl7.org/CodeSystem/data-absent-reason"/> 
      <concept> 
        <code value="asked-unknown"/> 
        <display value="Don't know"/> 
      </concept> 
    </include> 
  </compose> 
  <expansion> 
    <identifier value="urn:uuid:bf99fe50-2c2b-41ad-bd63-bee6919810b4"/> 
    <timestamp value="2015-07-14T10:00:00Z"/> 
    <contains> 
      <system value="http://terminology.hl7.org/CodeSystem/v2-0532"/> 
      <code value="Y"/> 
      <display value="Yes"/> 
    </contains> 
    <contains> 
      <system value="http://terminology.hl7.org/CodeSystem/v2-0532"/> 
      <code value="N"/> 
      <display value="No"/> 
    </contains> 
    <contains> 
      <system value="http://terminology.hl7.org/CodeSystem/data-absent-reason"/> 
      <code value="asked-unknown"/> 
      <display value="Don't know"/> 
    </contains> 
  </expansion> 
</ValueSet>