http://hl7.org/fhir/StructureDefinition/cqf-directReferenceCode|5.2.0

Indicates that the given code is directly referenced by artifact logic (e.g. as a [direct-reference code](https://cql.hl7.org/02-authorsguide.html#code) in CQL). Terminology dependencies used in logic can be collected and reported, typically using the relatedArtifact element with a type of `depends-on`. However, direct-reference codes cannot be represented in the relatedArtifact element, so this extension provides a means to support communicating direct-reference code dependencies of knowledge artifacts. As with value set dependencies, direct-reference codes may be the terminology target of a data requirement.