Worked on the geonetwork/core-geonetwork repository to deliver Group Owner Metadata Access Control, enabling group owners to access a new metadata field through a dedicated access filter type. The implementation involved updating XML serialization to enforce access control and integrating these changes across both core and API layers. Emphasized test-driven development by expanding unit test coverage to validate correct group owner access and ensure integration with existing APIs. Utilized Java for backend development, focusing on cross-module updates to XmlSerializer and EsHTTPProxy to maintain backward compatibility. The work established foundational governance for group-owned metadata and prepared for future role-based access controls.