HL7 OIDs and FHIR URIs

Question

I am new to the Health Level 7 standards and messaging paradigm and was reading up on OIDS/URIs. While I know OID are unique Identifiers assigned under an Assigning Authority, I would like to know the following:

1. If there any difference in their usage for V2 and V3 messages.
2. Whatis actually sent over the wire in terms of an OID?
3. Why is there a switch from OIDs to URIs in the context of the new HL7 FHIR standard?

Any help is appreciated.

Thanks

Answer 1

FHIR tries to move away from OIDs because of human readability:

Implementers strongly prefer a human readable URI. http://acme.com/patients/mrn is a great deal easier to work with than urn:oid:1.2.3.4.5.6.7

This text from the specification also answers your second question about the representation. You use the construct urn:oid: in those places, so the OID is represented as a URI.

Please take a look at https://www.hl7.org/fhir/terminologies.html for more information, and https://www.hl7.org/fhir/terminologies-systems.html and https://www.hl7.org/fhir/identifier-registry.html for a list of systems and their representation.