Comment:

A formal registry of profiles and extensions is important before FHIR is finalized. I couldn't locate a discussion of a registry or commitments to completing one before FHIR is normative.

A pilot project within DoD/VA IPO reviewed 3 profiles on Vital Signs, including C-CDA on FHIR. It became very clear that without a robust registry profile proliferation will occur. This proliferation will require each site and vendor to develop their own FHIR profiles and will recreate the HL7 V2 problem, customization for each new site.

Requirements may necessitate differences but it would be helpful to designers to highlight differences so only meaningful changes are introduced.