This model contains, in addition to the single-valued reference property
publisher representing the unidirectional many-to-one association Book-has-Publisher, the multi-valued reference property
authors representing the unidirectional many-to-many association Book-has-Author.
Recall that we obtain a Java Entity class, like
Author, from the corresponding class in the OO class model, by (1) making all properties private, (2) using Java datatype classes, (3) adding public getters and setters, (4) adding a
toString function, (5) adding the data storage methods
In the Java Entity class model, any reference property specified in the OO class model is annotated with the functionality type of the association represented by it. In our example, we annotate the reference property
authors in the Entity class