RELATIONs typically contain pairs of siblings (or cousins) at each level of the classification that are inverses of each other. They are classified into OBJECT-RELATION, EVENT-RELATION, EVENT-STATE-RELATION, EVENT-OBJECT-RELATION and their corresponding inverses. OBJECT-RELATIONs are those RELATIONs where the domain and range are both OBJECTs. They are divided into PHYSICAL-OBJECT-RELATIONs, MENTAL-OBJECT-RELATIONs, and SOCIAL-RELATIONs. SOCIAL-RELATION subsumes a range of interesting RELATIONs including ORGANIZATION-RELATIONs, CORPORATE-OBJECT-RELATIONs, SOCIAL-ROLE-RELATIONs (such as CORPORATE-RELATIONs, FIELD-OF-STUDY-RELATIONs, and PRODUCTION-RELATIONs).
EVENT-RELATIONs and EVENT-STATE-RELATIONs both pertain to relations between pairs of events. EVENT-OBJECT-RELATIONs subsume the important class of SPATIAL-RELATIONs. It may be noted that some MULTIPLE-ENTITY-SPATIAL-RELATIONs are in fact OBJECT-OBJECT relations although they have been placed under EVENT-OBJECT-RELATIONs. Since we do not use inheritance in PROPERTY hierarchies, their classification should be viewed merely as a convenient organization that is intended to help us locate the right property. The RELATION hierarchy is shown in Figure 12.
Figure 12:
Parts of the Classification of Relations in the Ontology.
Kavi Mahesh