If the asterisk is exchanged with its meaning, a regular English sentence is created: The name of one class is customer (1) the name of the other class is ticket (4). The appropriate values from the diagram have to be inserted into this first abstract formulation, which can be universally applied. One (this sentence always begins with “one”) object of the first class has an association with a number of objects of the second class.Looking at the class diagram in Figure 4.31, you can read the association between the classes customer and ticket as follows: Reading Class Diagramsįigure 4.31 shows a class diagram from our case study with the classes customer, ticket, and coupon, their attributes, and their associations: Figure 4.31 Class diagram with associations The diamond documents this meaning a caption is unnecessary. MultiplicityĪ multiplicity allows for statements about the number of objects that are involved in an association:Īn aggregation is a special case of an association (see above) meaning “consists of”: AssociationĪn association represents a relationship between two classes:Īn association indicates that objects of one class have a relationship with objects of another class, in which this connection has a specifically defined meaning (for example, “is flown with”). Refer to Generalization, Specialization, and Inheritance. Generalization is a relationship between two classes: a general class and a special class:
AttributeĪn attribute of a class represents a characteristic of a class that is of interest for the user of the IT system:Ĭharacteristics of interest of a passenger, for example, are name and age. In class diagrams, as shown in Figure 4.30, we work with the following elements: ClassĪ class represents a relevant concept from the domain, a set of persons, objects, or ideas that are depicted in the IT system:Įxamples of classes are passengers, planes, or tickets. Figure 4.30 Elements of the class diagram
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