The Usage Context (in the PIM the applicableContext) is represented as an attribute of the ConceptDomainBinding class. applicableContext - a realm or context in which the particular binding applies. If not present, the binding applies in any context not stated in another binding.
In the SFM it is represented as a class entirely apart providing detailed information about the binding. If we have two different value sets belonging to the same Concept Domain but with different usage contexts, this cannot work. Moreover, in most implementation guides, the Concept Domains are not specified, indicting just the Usage Context as Concept Domains are something very specific to HL7 (they can be inferred), and the Usage Contexts are expressed as OIDs and not as URIs (enforcing the fact that we need the possibility to simultaneously define an entity via an URI and an OID)
Use Case:
The value set epSOSActiveIngredient 1.3.6.1.4.1.12559.11.10.1.3.1.42.24 consists of the whole ATC and it is the most important piece of information in the medication identification in epSOS. The same value set is being used in 3 different documents in 4 different sections with 4 different entries:
Prescription Item Entry 1.3.6.1.4.1.12559.11.10.1.3.1.3.2
Dispensed Medicine Entry
1.3.6.1.4.1.12559.11.10.1.3.1.3.3
Medication Item Entry
1.3.6.1.4.1.12559.11.10.1.3.1.3.4
Allergy & Intolerance Concern Entry
1.3.6.1.4.1.19376.1.5.3.1.4.5.3
Prescription Section
1.3.6.1.4.1.12559.11.10.1.3.1.2.1
Dispensation Section
1.3.6.1.4.1.12559.11.10.1.3.1.2.2
Medication Summary Section 1.3.6.1.4.1.12559.11.10.1.3.1.2.3
Allergies and Other Adverse Reactions Section
1.3.6.1.4.1.19376.1.5.3.1.3.13
In the follwing documents:
ePrescription
eDispensation
Patient Summary
Patient Summary
The corresponding Concept Domain is EntityCode and the subdomain is ActiveIngredientDrugEntityType for all four Usage Contexts; however they are entirely different. Logged: https://github.com/cts2/cts2-specification/issues/146