A national digital twin is envisioned as an ecosystem where many twins are linked to a common foundation via mappings, yet the roadmap never defines what makes a mapping "valid". We formalize validity as coherence and conservativity of the merged ontology, borrowing concepts from logic‑based alignment repair, and apply the test to the Information Exchange Standard (IES).
Crosswalks from IES to thirteen ontologies across seven sector groups—anchored on BOT, Brick, and SAREF4BLDG—follow a pipeline of automatic matching, human review, certification of each SKOS correspondence against the two class hierarchies, and reasoning with the HermiT reasoner. Pair‑wise processing reveals different failure modes: certification alone eliminates 526 conservativity violations, review alone leaves 73, and together they make eleven of twelve overlapping pairs both coherent and conservative. Importantly, pairwise certification does not compose.
Merging the three certified building crosswalks into a single hub creates five unsatisfiable Brick classes due to a homonym between IES and Brick notions of a "floor"; only BOT’s disjointness axioms expose the conflict. Dropping that row restores a coherent and conservative hub that implicitly entails 290 cross‑ontology links not explicitly written.
Moreover, the core hub is inconsistent even before any crosswalk is added because the Open Energy Ontology and BFO 2020 contradict each other; removing either yields a coherent and conservative hub. Hence, the hub, not an individual pair, is the unit that a twin ecosystem must certify.
Review