[nradov]

That's why most interoperability requirements are written based on Implementation Guides rather than baseline standards. The base HL7 standards (V2 Messaging, CDA, FHIR) are intended to do pretty much everything everywhere in the world. As such, they're loose on specifics such as required data elements and coding systems. Then IG authors take those baseline standards and constrain them for specific use cases in particular countries (realms).

CCD is very well specified, although you might still find some EHRs that fail to comply with the standard in some minor ways. There is a project underway to migrate that data model to FHIR encoding but it's not finished yet; that will make document construction and parsing a bit easier but won't necessarily address compatibility issues.

https://www.hl7.org/implement/standards/product_brief.cfm?pr...

https://hl7.org/fhir/us/ccda/