A constructional theory of sets, parts and relations.

We develop a constructional approach to ontology, focusing on sets, parts and relations. On this conception of ontology, one starts with some constructors and an initial collection of objects. Then, new objects emerge by construction, that is, from the application of constructors to objects. This approach, which is inspired by work of Kit Fine, provides a unified formalization of core components of prominent formal ontologies. The resulting formal theory is also shaped by its intended application as a top-level ontology (TLO) for the Information Management Framework of the UK's National Digital Twin (NDT).