11.5. Roles
Each end of an association is called a role. Roles may optionally have:
name
multiplicity expression
navigability
Multiplicity is examined next, and the other two features are discussed in later chapters.
Multiplicity
Multiplicity defines how many instances of a class A can be associated with one instance of a class B (see Figure 11.3).
Figure 11.3. Multiplicity on an association.
For example, a single instance of a Store can be associated with “many” (zero or more, indicated by the * ) Item instances.
Some examples of multiplicity expressions are shown in Figure 11.4.
Figure 11.4. Multiplicity values.
The multiplicity value communicates ...
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