The RECONNECT project tackles the fragmentation in Ireland's public healthcare systems, aiming to improve service planning and delivery. It integrates complex systems within the Health Service Executive (HSE) for chronic disease management, prioritizes data privacy, and supports future digital resource integration. The methodology includes: (1) structural integration via a Federated Database design to maintain system autonomy while ensuring privacy; (2) semantic integration through a Record Linkage module to enable integration without individual identifiers; and (3) adoption of the HL7-FHIR framework for high interoperability, aligning with the national electronic health record (EHR) and the Integrated Information Service (IIS). The RECONNECT system is unique in Ireland, featuring a generic architecture for loosely coupled systems, adherence to HL7-FHIR for interoperability, efficient reuse of digital assets, and a robust privacy layer. A demonstration system using synthetic data from the Hospital Inpatient Enquiry (HIPE) and Chronic Disease Management (CDM) systems is implemented on Neo4j for visualization.