This is true whether the relationship is symmetric or asymmetric. Consider the following two cases. These relationships are symmetric and asymmetric, respectively. In both cases the relationship need be instantiated only once. In the latter case the order of the objects in the relationship is important.
Cardinality is a characteristic of the relationship in the context of the data under consideration.
A number of houses may be on a given street. Copyright 2001 Government of British Columbia. All rights reserved.