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.

Figure 8.6. The Publisher-Book information design model with a unidirectional association

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 Book and Author shown in Figure 8.7 below, models a multi-valued reference property authors.

Figure 8.7. The Publisher-Book-Author information design model with two unidirectional associations