IfcRelationship is the abstract generalization of all objectified relationships in IFC. Objectified relationships are the preferred way to handle relationships among objects. This allows to keep relationship specific properties directly at the relationship and opens the possibility to later handle relationship specific behavior. 

There are two different types of relationships, 1-to-1 relationships and 1-to-many relationship. used within the subtypes of IfcRelationship. The following convention applies to all subtypes:

• The two sides of the objectified relationship are named Relating+and Related+
• In case of the 1-to-many relationship, the related side of the relationship shall be an aggregate being a set 1:N

This definition may not be instantiated.