This is intended as a strawman for comment.
This is proposing using HL7v2 Messaging (v2.4) as a basis for FHIR Messaging. This obviously aids compatibility in mixed economies.
The primaryFocus column indicates the main data items that are being exchanged and correspond to FHIR RESTful interactions e.g. Encounter message may become a POST /Encounter.
Initial focus is proposed to be on lightweight notifications , i.e payloads are minimal. It in not meant to be a mechanism for transferring data (so in Hl7v2 terms, push for focus on R Required and not O Optional segments).
Some workflow messages are included as they are being developed (prescription-order and pathology unsolicited-observations).
I’m tempted to add in patient-referral (focus ServiceRequest REF_I12) but feel that may add complication (plus needs a bit of Hl7v3 analysis)