FHIR Terminology Service specification describes a set of operations on CodeSystem, ValueSet and ConceptMap resources. Among those operations, the following four operations appear to be the most widely adopted ones:
Developing a partial implementation of the specification has been an effective way to explore the new FHIR framework introduced in IRIS for Health 2020.1. The implementation includes four operations listed above, and supports read and search interactions for CodeSystem and ValueSet resources.
It's important to note that the implementation uses plain ObjectScript persistent classes as source terminology tables.