Instead, each type is defined in relation to the other types in the lattice. This is exactly what is done in Euclidian geometry in which points, lines and places are defined by virtue of the five postulates, or in physics in which particles, fields and forces are defined by virtue of the equations in which they participate. New types and relations can be defined using these constructions. Multiple lambda variables are used to define new relations. An organic chemical is a chemical that is carbon-containing.
Care is an activity in which a provider treats a patient.
The UMLS Semantic New can be considered an informal ontology for medicine. The types are ordered as a tree, but the distinctions are not given, thus it is impossible to construct a lattice for the types. Textual definitions are given for each type and relation, but no defining distictions or axioms are provided, so there is no formal way to classify new individuals. The semantic net specifies which relations are permissible between pairs of semantic types, but does not indicate which are necessary and which are merely optional. Under Event, there is a split into Phenomenon or Process and Activity, which both appear to be physical.