I designed, implemented, and supported 5 regional exchanges. Interop is always case-by-case. Protocols like HL7 (2.x, 3.x, FHIR) give you shared syntax (lexing

I designed, implemented, and supported 5 regional exchanges. Interop is always case-by-case. Protocols like HL7 (2.x, 3.x, FHIR) give you shared syntax (lexing) and about 98% agreement on structure and semantics (parsing). Then you'll spend most time on the last 2% on excruciating details. Data quality on field values, matching units, mapping one taxonomy to another (and back). > If users configure the software incorrectly... Based on my experience, incompatibility is a given. Regardless of the cause. Misconfiguration, mismatched versions, ignorance, artistic license, etc. Plan for the worse, hope for the best.