The model shown in Figure 8.6 below (about publishers and books) serves as our running example for a unidirectional functional association. Notice that it contains the unidirectional many-to-one association Book-has-Publisher.
We may also have to deal with a multi-valued reference property
representing a unidirectional non-functional association. For instance,
the unidirectional many-to-many association between
Author shown in Figure 8.7 below, models a multi-valued reference