Components of Ontologies

The following are the components of Ontologies:

• Concepts: These are the general things or entities similar to classes in object-oriented programming, for example, a person, an employee, and so on.
• Slots: These are the properties or attributes of the entities, for example, gender, date of birth, location, and so on.
• Relationships: These represent interactions between concepts, or is-a, has-a relationships, for example, an employee is a person.
• Axioms: These are statements which are always true in regards to concepts, slots and relationships, for example, a person is an employee if he is employed by an employer.
• Instances: These are the objects of a class in object-oriented terms. For example, John is an instance of the Employee class. It is a specific representation of a concept. Ontology, along with instances, fully represents knowledge.
• Operations: These are the functions and rules that govern the various components of the Ontologies. In an object-oriented context, these represent methods of a class.

The following diagram explains the components of Ontologies:

The development of Ontologies begins with defining classes in the Ontology. These classes represent real-world entities. Once the entities are clearly identified and defined, they are arranged in a taxonomic hierarchy. Once the hierarchy is defined, the Slots and Relationships are defined. Filling in the values for slots and instances completes the development of a domain-specific Ontology.