Class (knowledge representation)

In knowledge representation, a class is a collection of individuals or objects.[1] A class can be defined either by extension (specifying members), or by intension (specifying conditions), using what is called in some ontology languages like OWL. According to the Type–token distinction, the ontology is divided into individuals, who are real worlds objects, or events, and types, or classes, who are sets of real world objects. Class expressions or definitions gives the properties that the individuals must fulfill to be members of the class. Individuals that fulfill the property are called Instances.

Main article: Classes on the ontology component page

Relationships

Instantiation

The instantiation relationship is a relation between objects and classes. We say that an object O, say Harry the eagle is an instance of a class, say Eagle. Harry the eagle has all the properties that we can attribute to an eagle, for example his parents were eagles, he's a bird, he's a meat eater and so on. It's a special kind of is a relationship. It's noted Concept assertion () in Description logics, a family of logic based on classes, class assertion [2]

Subsumption

Classes can subsume each other. We say usually that if A and B are classes, and all A instances are also B instances, then B subsumes A, or A is a subclass of B, for example in the OWL Language it's called subclassof.[2]

gollark: If it was possible to run multiple emulated CC instances with peripherals and networking and such, that would be *really* convenient for development.
gollark: I am somewhat glad we did not get annoying hovery interaction.
gollark: Please put \` \` \` lua (without the spaces) around your code instead of just `.
gollark: What does that mean?
gollark: The bundled cable thing actually works between two computers which are next to each other *even without any actual bundled cable mod*.

References
  1. Diego Calvanese; Giuseppe De Giacomo; Maurizio Lenzerini (2002). Description Logics: Foundations for Class-based Knowledge Representation. Logic in Computer Science.
  2. "owl2 syntax".

See also
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