Visibility is used to signify who can access the information contained within a class denoted with +, -, # and ~ as show in the figure: GeneralizationĪ generalization is a relationship between a general thing (called the superclass) and a more specific kind of that thing (called the subclass). For example, one company will have one or more employees, but each employee works for one company only. These symbols indicate the number of instances of one class linked to one instance of the other class. Place multiplicity notations near the ends of an association. Associations are always assumed to be bi-directional this means that both classes are aware of each other and their relationship, unless you qualify the association as some other type.Ī bi-directional association is indicated by a solid line between the two classes. Unidirectional association - In a unidirectional association, two classes are related, but only one class knows that the relationship exists.Ī unidirectional association is drawn as a solid line with an open arrowhead pointing to the known class.īidirectional (standard) association - An association is a linkage between two classes. In a class diagram, an association relationship is rendered as a directed solid line. In an association relationship, an object of the whole class has objects of part class as instance data. Association specifies a "has-a" or "whole/part" relationship between two classes. Some objects are made up of other objects.
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