Object Properties

An object property is a binary relation between two individuals that lets you assert general facts about the members of classes and specific facts about individuals. Characteristics of a property are defined by so-called property axioms. In its simplest form, a property axiom just defines the existence of a property. However, property axioms often define additional characteristics of properties. OWL supports the following constructs for property axioms:

These language constructs are distributed to the following tabs in the Entity Properties panel:

For instructions on how to create an object property, see Create an Object Property.

Online References

Further information is available at the following Web sites:

Domain and Range

The notions domain and range have meanings inspired by the mathematical uses of these terms. In mathematics, they are used to refer to how a function can be used. The domain of a function is the set of values for which it is defined, while the range is the set of values it can take. Similarly in OWL, if you specify a class D as the domain of the property P and class R as the range of P, the informal interpretation of this is that the Property P relates values from the class D to values from the class R.


Note – Use domain and range declarations with care. It is important to realize that in OWL domain and range declarations do not act as constraints to restrict the relation. It is tempting but not correct to think of rdfs:domain as the class of objects to which a property can be applied. Instead, it is used as an axiom for reasoning purposes. For example, any individual that uses a property with a given domain can be inferred by the reasoner to be a member of the domain class, for the statement P rdfs:domain D just means that all things to which P is applied can be inferred to be a member of class D. This, on the other hand, can lead to unexpected classification results and side effects, especially in situations when multiple ontologies may be merged. Therefore, consider not setting any domains and ranges and using local class restrictions instead.

In addition to simple classes you can also enter complex classes using the Manchester Syntax. Note that selecting multiple domains means that the domain of the property is the intersection of the classes (and similarly for range).

Characteristics

Additionally, OWL allows the meaning of properties to be enriched through the use of property characteristics.

The Characteristics section contains two sets of check boxes. The left set is changeable and represents the assertions of the current ontology. The set on the right hand side, labeled transitive closure, cannot be changed and represents also assertions that come from imported ontologies.

OWL Object Property

Taxonomy
On this tab you can specify relations to other properties. This includes the following settings:

OWL Object Property

Annotations

Usually, annotations are used to add information to resources of the ontology. They contain useful information such as who is the creator or what are the readable labels and comments for single elements of the ontology.

For information on how to create an annotation, see Create an Annotation.

OWL Object Property