Functional and Communicative Interoperability in European Healthcare Systems: A Comparative Overview of HL7 FHIR, openEHR and OMOP

This study investigates the extent to which the HL7 FHIR1, openEHR2, and OMOP3 medical data models contribute to operational interoperability in European clinical care networks. Using a methodical document analysis, four countries – Estonia, Denmark, Finland, and Germany – are compared according to defined analysis parameters. The results show clear differences in the degree of integration, institutional control, and IT integration. Beyond technical data transfer, the study defines conceptually functional system interoperability as an information process of communication and organisation embedded in governance structures, institutional coordination, and regulated information flows. While Estonia and Finland have hierarchically organized IT systems with a high degree of integration, Germany has decentralized structures. The study shows that the effectiveness of interoperable standards depends not only on their technical specifications but also on their regulatory, administrative, and systemic integration. This has direct relevance for the development of evidence-based, intelligent care systems within the European Health Data Space. The paper shows that operational interoperability should be viewed as a structural concept that requires multidisciplinary coordination strategies. The results can, in principle, support future interoperability projects – especially in the country-specific adaptation of electronic care platforms.