An interoperability framework specifies the tools for achieving the exchange of EHR data between healthcare providers nationally or at a world-wide level. Following the European Commission (EC) recommendation announced in 2019 about the consideration of the possibility offered by resource driven information models (offered by HL7 FHIR) for the refinement of the exchange format of the EHRs [9],  the FHIR standard was thoroughly studied, evaluated and selected for implementing interoperability in eHealth4U. ​

Another provision of the eHealth4U interoperability framework is the capture of citizens’ health data in a structured form to facilitate its integration with various 3rd party systems in the national eHealth ecosystem (e.g. public health monitoring systems, etc.). FHIR implementations incorporate structured data allowing resources’ elements to have coded values. In eHealth4U, priority is given in exploiting the fixed value sets provided by FHIR specification. The terminologies of SNOMED CT, ICD-11 and LOINC have been used to create value sets where FHIR specification did not fulfill the project’s requirements. Finally, where none of the previous two solutions is applicable, a new code system is created based on the specific project’s requirements. In addition, a mapping between the EHR fields and the FHIR profiles’ elements was made using SNOMED CT, ICD-11 and LOINC. ​