CTS2-LE Loader: FHIR

This section describes the structural and semantical aspects of a FHIR value set definition. Furthermore, the CTS2-representation of a FHIR value set (which directly reflects the resulting structure of an integrated value set) is illustrated. A background on FHIR, web technologies and CTS2 entities is assumed since these subjects will not be presented in detail.

FHIR and CTS2

FHIR and CTS2 employ slightly different notions for value sets: Within FHIR, "A value set can define its own codes, and/or a value set can be composed of codes defined in other code systems, either by listing the codes or by providing a set of selection criteria […] Value set resources can be converted to CTS2 value set and code system resources." CTS2 explicitly distinguishes between value sets ("a set of entity references" ) and code systems ("a collection of codes or identifiers […] used for reporting, organizing, and/or reasoning about knowledge in some discipline, specialty, or domain"). When wanting to be precisely, either the suffix “FHIR” or “CTS” is given to indicate the indented meaning.

FHIR value set definition file

<ValueSet xmlns=”http://hl7.org/fhir”
	xmlns:ext="http://semantik.fokus.fraunhofer.de/ehealth/fhir-extensions#">
	<!-- in general, FHIR-extensions are used for items currently not present 
	in FHIR. Then namespace http://semantik.fokus.fraunhofer.de/ehealth/fhir-
extensions#" (see above) has to be used -->
	<!-- Attention: when 'defining' a code system, the 'identifier' element 
	is not used/relevant because the defined code system is identified by 
'<define>/<system>' below; we do not build a wrapping VS so far -->
<identifier value="[string]" />
<!-- group corresponding to the terminology tree in the navigator: -->
<extension url="ext:groupName">
	<valueString value="[string]" />
</extension>
<version value="[string]" />
	<!-- A free text natural language name describing the value set (in case 
	of 'define' this will be internal name of the code system displayed in the 
	navigator) -->
<name value="[string]" />
<publisher value="[string]" />
<telecom></telecom>
<!-- A free text natural language description of the use of the defined 
code system or value set - reason for definition, conditions of use, etc.: -->
<description value="[string]" />
<copyright value="[string]" />
<status value="[code]" />
<experimental value="[boolean]" />
<extensible value="[boolean]" />
<date value="[dateTime]" />
<!-- for CTS code system import -->
<define>
<!-- IETF language tag (RFC 5646) restricted to 2-letter tags; so far 
not checked; only relevant when 'define' a code system -->
	<extension url="ext:language">
		<valueCode value="[string]" />
	</extension>
	<!-- URI to identify the code system -->
	<system value="[uri]" />
	<version value="[string]" />
	<caseSensitive value="[boolean]" />
	<concept>
		<code value="[code]" />
		<abstract value="[boolean]" />
		<display value="[string]" />
		<definition value="[string]" />
		<!-- nest concepts for sub-classing -->
                <concept>
	        </concept>
	</concept>
</define>
<!-- for CTS value set import -->
<compose>
	<import value="[uri]" />
	<include>
		<system value="[uri]" />
		<version value="[string]" />
		<code value="[code]" />
		<filter>
			<property value="[code]" />
			<op value="[code]" />
			<value value="[code]" />
		</filter>
	</include>
	<exclude>
	</exclude>
</compose>
<!-- for CTS value set export -->

</ValueSet>

As mentioned earlier, FHIR value sets may be mapped to either CTS code system or CTS value sets. The output is determined by the existence of the elements define and compose: a define-element leads to a code system (more precise: CodeSystemVersionCatalogEntry) being imported whereas compose hints that a value set (ValueSetDefinition) is the target CTS entity. Note that the current setting does not allow an import of definition files which contain both a define and a compose-element.