Top ontology and domain ontologies

A domain ontology describes details of a particular domain. Examples of domain ontologies are a biomedical ontology (or even more specific, only about neurology), or an ontology about airports.

In contrast, a top ontology (synonyms: upper ontology, top-level ontology, foundation ontology) “describes very general concepts that are the same across all domains. The aim is to have a large number on ontologies accessible under this upper ontology.” (Mascardi et al. (2007) A Comparison of Upper Ontologies)

SUMO# and Cyc# are big, well-known top ontologies. Mascardi et al. list other big ones (in 2007). Wikipedia has a more up-to-date list.1.

Purpose of top ontology

Breuker and Hoekstra (2010) list two roles for an upper ontology.

1. Structure of classes for domain ontologies to attach to

In the following picture, the domain ontologies of Neurology and Airports are connected to an upper ontology, which starts from very generic terms. (Made-up example, not from any real ontology.)

          Entity
          /  |  \
        … … … … … …
    Biology  …  Geography
    / | | \ … … / | | \
 … … … … … … … … … … … … …
     |                 \
  Neurology           Europe
  / | | \            /   |  \
 … … … … … … … … … … … … … … …
 |                         |
Optic nerve          Heathrow airport

2. Properties for free thanks to inheritance

For instance, say that a core ontology has a class PhysicalObject and includes axioms such as physical objects have a mass and they leave a shadow. Then a domain ontology about furniture hangs its concepts under an appropriate subclass, and all of its chairs and tables get the properties of having a mass and leaving a shadow.

Core ontology

The term core ontology is sometimes used. If I (Inari) have understood correctly, a core ontology is sort of an upper ontology for a domain. So a true upper ontology is super generic, starting from Entity, core ontology would start from the most general concepts for a given field, like (for legal domain) legal role, process, place, time, etc.

Some legal core ontologies are listed in Legal ontology#.

  1. Heuristic of relevance: does the ontology have its own Wikipedia page. Wikipedia remarks “Note that the lack of fresh releases does not imply inactivity or uselessness.” This is true especially for an upper ontology. The purpose is to be compact and general, and that kind of information doesn’t need to be updated.

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