How for I search fhir resources based on extension values?

Question

I have a set of fhir resources in the following form:

<Basic>
    <meta>
      <versionId value="1.0"/>
      <lastUpdated value="2016-11-18T10:26:51Z"/>
      <profile value="http://stelar.org/StructureDefinition/stelar/profile/anthropometry"/>
    </meta>
    <text>
      <status value="generated"/>
    </text>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/const-sourceIdentifier">
      <cohortName value="TEST"/>
      <datasetName value="SEATONJEAug14A1"/>
      <archetypeName value="Abdo20wks"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/const-resourceTags">
      <valueString value="SEATON"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/anthropometryType">
      <valueCoding value="AnthropometricMeasure"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/subjectNo">
      <valueString value="5375"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/methodOfFollowUp">
      <valueCoding value="FollowUpMethod.ClinicVisit"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/followUp">
      <valueCoding value="FollowUp.SNRecruitment"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/variableLabel">
      <valueString value="Abdominal girth 20 week fetal scan (mm)"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/AIW">
      <valueDouble value="1841.0"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/subject">
      <valueCoding value="Person.StudySubject"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/clinicalType">
      <valueCoding value="ClinicalMeasurement.AnthropometricMeasure"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/dataSource">
      <valueCoding value="DataSource.ClinicalMeasurement"/>
    </extension>
    <extension url="http://stelar.org/StructureDefinition/stelar/extension/dataAnthropometricMeasure"/>
</Basic>

I have many similarly structured resources where a few constants change on them, such as the value of http://stelar.org/StructureDefinition/stelar/extension/dataSource. How would I go about constructing a query to search for resources which had a dataSource of 'DataSource.ClinicalMeasurement'.

I've read the documentation about searching, however there doesn't seem to be any mention of searching extensions.

As a side note I've had to base all of my data around the Basic resource type and use extensions for reasons that are a bit too unrelated to bring up here.

Answer 1

You can define your own SearchParameter instance that defines how to query using any element or combination of element - extension or core. And you can use your server's Conformance resource to identify the SearchParameters you support and what names should be used for those search parameters.