HL7v3 vs FHIR

3 minute read


I prepared this contents based on the research, I made on the particular topic. So I just some basic clarification on similarities and Dissimilarities for my project @ internship.

HL7 Version 3 is based on the RIM model, and FHIR is the new approach that is released in 2018. The draft is released in 2014 for testing the Model.

Summary on HL7v3 VS FHIR

Model :

HL7 RIM is the core for v3(ISO also), while FHIR doesn’t rely much on it thus it can be developed without knowledge of RIM. But it has features that contain those based on RIM.

Code :

In v3 attributes are controlled by HL7 and in FHIR it is controlled by business meaning example (contact types, status). Both of them make use of valueset but for FHIR valueset is also another data type, thus it can be sent as a part of data
(The same is true of StructureDefinition, Conformance, and other meta-level resources.)

Granularity :

v3 divided into 3 main types wrappers, payload, Common Message Element Types (CMET). for reusing existing, but FHIR is divided for making use with “standalone”. For v3 we have a different schema for a single data type while FHIR has the only single data type

Design by constraint :

It is hard to design an abstract model for a system, especially the health care system, we can model to about 80 - 90 percentage, the “80 percent rule” was applied on FHIR, to support at least 80 percent supportive and others will be added based on the extension. while v3 is based on domain-specific, and it becomes less abstract when it move tends to the implementer. for here we need to produce each schema, and it is not always wire compatible.

Context conduction :

In v3 for an example a report is responsible for a doctor, it will tell him as the author, and while processing analysis through the system it will concern with the particular author, while in FHIR it is vice versa, it will deal with the patient, not to affect just an id to store.

Null flavors :

It is to notify null in place of missing values, while in FHIR it is only for core requirement


  1. https://www.hl7.org/fhir/comparison-v3.html
  2. https://en.wikipedia.org/wiki/Health_Level_7

2 and 3 are for additional study, it is for comparison of v2 (the most used version and comparatively best fit with FHIR than v3), CDA (it is best fit in the sense of human readability but limited to only clinical matters not financial and others), CCD (medical summaries of persons ), SPL (information about medicine) and CCOW (to share the user context among application)

Note these CDA, CCD, SPL, CCOW are released alongside version 3 and it was expected to improve on specific occasions and also human readability.



  1. FHIR - Fast Health Interoperability Resources.
  2. RIM - Reference Information Model
  3. CDA - Clinical Document Architecture
  4. CCD - Continuity Care Document
  5. SPL - Structured Product Labeling
  6. CCOW - Clinical Context Object Markup