Achieving seamless data integration (DI) and semantic interoperability (SI) is essential in the healthcare sector and demands patient-centric data that is readily accessible and shared unambiguously across health information systems (HIS). The complex landscape of federated IS highlights auspicious challenges for DI and SI stemming from diverse data sources and formats. The authors showcase a hybrid ontology-based design science research engineering (ODSRE) methodology that combines design science activities with ontology engineering principles and employs Ontop to develop the stateof-the-art federated virtual knowledge graph (FVKG) framework embedded with the virtual knowledge graph (VKG) approach to handle the aforementioned challenges effectively. The proposed FVKG facilitates a unified virtual view of dispersed data sources and diverse models, forming a virtual data federation that effectively addresses data bottlenecks using the Ontop semantic query engine. Using virtual techniques, the FVKG reduces data migration, ensuring low latency and freshness, and facilitates real-time access while upholding integrity and coherence throughout the federation system. As a result, authors suggest a customized hybrid framework for constructing ontological monolithic semantic artifacts, especially in HIS. The FVKG incorporates ontology-based data access (OBDA) to build a monolithic virtual ontological model, integrating various ontology-driven artifacts and ensuring semantic alignment using schema mapping techniques.