Theodoridou, MariaHivert, FlorianKritsotaki, AthinaMarkhoff, BéatriceDoerr, MartinHermon, SorinCampana, StefanoFerdani, DanieleGraf, HolgerGuidi, GabrieleHegarty, ZackaryPescarin, SofiaRemondino, Fabio2025-09-052025-09-052025978-3-03868-277-6https://doi.org/10.2312/dh.20253325https://diglib.eg.org/handle/10.2312/dh20253325The paper presents the definition of the ECHOES Heritage Digital Twin Ontology for cultural heritage. It is built upon the data model HDTO, improving and clarifying it with respect to the ECHOES Project objectives. ECHOES aims at setting up the European Collaborative Cloud for Cultural Heritage (ECCCH), a shared platform designed to facilitate collaboration among heritage professionals and researchers. The ontology is being developed as a compatible extension of the ISO 2117:2023 CIDOC CRM standard for cultural heritage documentation.Attribution 4.0 International Licensedigital twin, heritage documentation systems, CIDOC CRM extensiondigital twinheritage documentation systemsCIDOC CRM extension10.2312/dh.202533255 pages