This paper argues that interoperability in European cultural data infrastructures is not primarily a semantic modelling problem but a governance and rights-design challenge. While digital humanities scholarship has focused extensively on ontologies, linked open data, and technical interoperability, less attention has been paid to the legal, organisational, and curatorial architectures required to sustain such systems at continental scale. Heritage Digital Twins (HDTs), central to the emerging European Collaborative Cloud for Cultural Heritage (ECCCH), make these structural tensions particularly visible.

Drawing on the implementation of the Finno-Ugric Data Sharing Space (DSS) within the ECHOES framework, the paper extends earlier ontological pattern–based methodology into governance-aware digital twin deployment. Rather than proposing a new ontology, we operationalise and stress-test the Heritage Digital Twin Ontology (HDTO) in small-scale, multilingual heritage ecosystems dispersed across multiple national jurisdictions. In this environment, shallow archival depth, historically layered translations, dispersed custodianship, and uneven documentation practices shift the core challenge from schema alignment to authority reconciliation, rights clarification, and publication-boundary modelling.

Musical recordings, audiovisual materials, and ethnographic artefacts in these contexts involve layered authors’ rights, neighbouring rights, moral rights, personality rights, and, in some cases, Indigenous (CARE) considerations. We demonstrate that these rights layers must be encoded as structural components of digital twin models rather than treated as external compliance constraints.

Aligned with the European Interoperability Framework, we propose a governance-first architectural pattern integrating legal, organisational, semantic, and technical layers. The findings suggest that digital twin implementation can function as an interoperability catalyst: by formalising governance constraints, semantic alignment becomes operationally tractable. The paper contributes a framework for legally robust, sustainable, and AI-ready cultural data infrastructures that enables small and multilingual heritage ecosystems to participate in European data spaces without centralising control or erasing community agency.