Ontology

An explicit model of a domain's entities, relationships, properties, and equivalences across systems. It makes it possible to state that two different identifiers or labels represent the same organization, contract, or person, and to make those decisions reviewable by people who understand the business.

Ontology handles identity and relational meaning; it does not calculate metrics by itself or automatically enforce authorization. The hard work lies in modeling and maintenance: sources diverge, identities change, and exceptions emerge. Without an owner, reconciliation criteria, and provenance for relationships, a graph can merely formalize an incorrect interpretation.