Existing Wording: Profiling

Comment:

It is common that resource references should be constrained such that they resolve to a profiled resource, rather than a base resource. For example, in the US realm, wherever there is a reference to Patient, that reference should be restricted to a DAF-Patient. So any resource that references Patient will need to be profiled, to impose this restriction. For example, we have to profile NutritionOrder, whether that was in the original scope or not. Now, since ClinicalImpression refers to NutritionOrder, and we don't want to point to the unprofiled version of NutritionOrder, we have to create a profile of ClinicalImpression that restricts the reference to NutritionOrder to our new profiled version. And so on, and so on. Considering the entire network of relationships between resources in FHIR, profile developers end up having to profile most or all resources (the only exception being loosely connected or unconnected "islands" such as the billing and payment resources. Strictly speaking, any reference to "Any" immediately entails profiling every resource.)

The fan-out problem implies creating a great many profiles (a network covering set), and changing all the resource references in those profiles. With the current tooling, this is an imposing task. For QICore, tackling the fan-out profile took about 40 person-hours of mind-numbing work.