3.1 Concept types

Introduction and sample ontology

The concept type of a concept says what kind of concept we are dealing with. For example, these could all be types in our ontology:

   Entity > Bus, Person, Tree, Location, Act, Animal.
   Person > Student, Employee.
   Employee > Professor.
   Tree > SycamoreTree.
   Location > City.
   Act > Go, Leave, Eat, Catch.
   Animal > Cat, Dog, Bird, Mouse.

What is a type?

A type is a label or name we give to a group of entities with similar traits. If we can categorize a number of individuals (e.g., "John", "Alfred", "Mary") in the same group (e.g., "Person"), then we can call the name of the group, together with the definition of the group, a "type".

Subtypes and supertypes

A type can be a subtype of another type. For example, in the above ontology, "Cat" is a subtype of "Animal", while "Student" is a subtype of "Person". In the list of examples above, subtypes are listed after their supertype and a '>'.

Lattice notation

The concepts "subtype" and "supertype" will become clearer if we look at the above examples of types in a diagram such as this:

"Some of the above types, drawn in a lattice"

Here, we see that the "subtypes" are below their "supertypes". The Entity and Absurdity types will be explained later.

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