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Upper ontology

Definition

An upper ontology — also called a top-level ontology or foundational ontology — is an ontology that defines the most general concepts and relations used across multiple narrower (domain / subject-matter) ontologies. It is meant to be shared, so that domain ontologies built on top of it are automatically interoperable through the common root.

Wikipedia's framing of upper ontologies is the one the UDA post links to: upper ontology.

Classical upper-ontology examples from the semantic-web / knowledge-representation tradition include BFO, DOLCE, SUMO. These are theoretical / philosophical / standardisation artefacts, not production systems.

Netflix Upper as a production upper ontology

Netflix's Upper is the wiki's canonical instance of an upper ontology designed for production enterprise data integration. Per the UDA post (sources/2025-06-14-netflix-model-once-represent-everywhere-uda):

"Upper is the metamodel for Connected Data in UDA — the model for all models. It is designed as a bootstrapping upper ontology, which means that Upper is self-referencing, because it models itself as a domain model; self-describing, because it defines the very concept of a domain model; and self-validating, because it conforms to its own model."

Three distinguishing features of Upper-as-upper-ontology vs the classical tradition:

  1. Bootstrapping. Upper is self-referencing — it models itself as a domain model, and the runtime treats it as such. This is patterns/self-referencing-metamodel-bootstrap.
  2. Production substrate, not theoretical standard. Upper exists to drive transpilation (domain model → GraphQL / Avro / SQL / RDF / Java), not to capture the grand structure of reality.
  3. Composition by conservative extension. "All domain models are conservative extensions of Upper" — Netflix's domain models grow by monotonic addition on top of Upper, ensuring the global semantics stay consistent.

Upper also deliberately restricts + generalises the W3C stack: "It defines a strict subset of semantic technologies from the W3C tailored and generalized for domain modeling. It builds on ontology frameworks like RDFS, OWL, and SHACL so domain authors can model effectively without even needing to learn what an ontology is."

Upper ontology vs metamodel

These two concepts overlap + converge in UDA:

  • An metamodel is a model of models — a specification whose instances are other models.
  • An upper ontology is a model of the most general concepts + relations shared across domain ontologies.

Upper is both at once: it is the metamodel whose instances are domain models, and its top-level vocabulary is what all domain models extend. The two framings name the same artifact from different angles.

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