FHIRconnect: Towards a seamless integration of openEHR and FHIR

Healthcare interoperability between openEHR and HL7 FHIR remains challenging due to fundamental differences in their data modeling approaches and the absence of standardized transformation mechanisms. This paper presents FHIRconnect, a novel domain-specific language and open-source transformation engine that enables standardized, bidirectional data exchange between openEHR and FHIR. Our approach addresses critical interoperability gaps through a triple-layered architecture that achieves 65% mapping reuse across projects by leveraging international archetype-based foundations while supporting local customizations. Using this framework, FHIRconnect successfully mapped 24 international archetypes to 15 FHIR profiles across seven clinical domains. Key contributions include the first comprehensive DSL for openEHR-FHIR transformation with a formal specification, an open-source execution engine (openFHIR), and an accessible mapping library covering high-impact clinical archetypes. Together, these components establish the technical basis for community-driven mapping standardization, reducing reliance on custom ETL solutions and advancing syntactic and semantic interoperability in healthcare IT systems built on open standards.