Example Simple Extension

Simple Extension

Adding a single extension to a resource.

Standard disclaimer: These extensions are contrived for the purpose of illustrating syntax. DO NOT assume that the content exists or is useful in any particular context!

In the instance

<Patient xmlns="http://hl7.org/fhir">
...snip...
	<!-- Add a "Do Not Call" flag to a Patient record.  -->
	<extension url="http://example.com/fhir/StructureDefinition/patient-do-not-call">
		<valueBoolean value="false"/>
	</extension>
...snip...

The extension profile

An extension profile

• Extends the HL7 Extension type
• Fixes all url elements (Element.url and any sub-element element.url paths)
• Constrains as appropriate the value[x] element

The differential (what's different from Extension):

<differential>
	<element>
		<path value="Element.url" />
		<fixedUri value="http://example.com/fhir/StructureDefinition/patient-do-not-call" />
	</element>
	<element>
		<path value="Element.value[x]" />
		<!-- Require the value if desired. -->
		<min value="1" />
		<!-- Limit the value type to boolean -->
		<type>
			<code value="boolean" />
		</type>
	</element>
</differential>

The Resource Profile

The extension can then be added to a profile as a known/expected extension. This is as simple as adding a slice of extension to the profile.

When adding an extension to the profile:

• Assign a name to the extension (as a named slice of extension).
• Constrain the type of the profile to the extension profile (using the extension profile's URI)

There is no need to add an additional information to the resource profile - the value[x] and/or any sub-extension will be pulled in from the extension profile.

<differential>
	<element>
		<path value="Patient.extension" />
		<name value="doNotCall" />
		<type>
			<code value="Extension" />
			<profile value="http://example.com/fhir/StructureDefinition/patient-do-not-call" />
		</type>
	</element>
</differential>