Ontology Design

An ontology defines the vocabulary: the classes (Person, Drug, Disease), the predicates (TREATS, CONTRAINDICATED_FOR), and the rules — domain and range constraints like 'TREATS runs Drug→Disease, never the reverse.' In RDF ecosystems, OWL ontologies are enforced by reasoners that infer triples you never wrote (Socrates IS_A Man + Man SUBCLASS_OF Mortal ⊢ Socrates IS_A Mortal). In property graphs, the contract is enforced by convention and validation code.

Either way the payoff lands downstream: queries written against TREATS keep working regardless of who loaded the data. Without the contract, every consumer reverse-engineers your pile.