I am working on a solution for the HRRP hospital readmissions reduction program.
I want to make my server FHIR compliant. But what does FHIR compliant mean? My HRRP solution has some data that does not match any of the pre defined resources. For example, the HRRP solution involves calculating scores like readmission ratio, payment etc.
As a FHIR server, FHIR conformance means that you expose a Conformance/CapabilityStatement at the "meta" URL on your endpoint and that you do whatever that statement says. Technically, you can be a FHIR-conformant server if all you do is expose a CapabilityStatement that declares that you don't support REST or messaging or services or documents. But you probably won't get much market share . . .
From an interoperability perspective, it'll often be more useful to claim conformance with a particular Conformance statement from an implementation guide than to declare conformance with FHIR overall. (Implementation Guides will be much more strict about exactly what behaviors are desired. FHIR can't do that because FHIR is so broad there's simply too many different possibilities.)