Multiplicity Indicators

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Although multiplicity is specified for classes, it defines the number of objects that participate in a relationship. Multiplicity defines the number of objects that are linked to one another. There are two multiplicity indicators for each association or aggregationone at each end of the line. Some common multiplicity indicators are

1	Exactly one
0..*	Zero or more
1..*	One or more
0..1	Zero or one
5..8	Specific range (5, 6, 7, or 8)
4..7,9	Combination (4, 5, 6, 7, or 9)

CREATING MULTIPLICITY IN RATIONAL ROSE

1. Double-click on the relationship line to make the Specification visible.

2. Select the Detail tab for the role being modified (Role A Detail or Role B Detail).

3. Enter the desired multiplicity in the Cardinality field.

4. Click the OK button to close the Specification.

Multiplicity indicators are shown in Figure 6-7.

Figure 6-7. Multiplicity Indicators

The drawing in Figure 6-7 may be read in the following ways:

• One CourseOffering object is related to exactly one Professor object playing the role of the Teacher. For example, Math 101, Section 1 (a CourseOffering object) is related to Professor Smith (a Professor object).

• One Professor object playing the role of the Teacher is related to zero to four CourseOffering objects. For example, Professor Smith (a Professor object) is related to Math 101, Section 1; Algebra 200, Section 2; and Calculus 1, Section 3 (CourseOffering objects). Since the multiplicity is a range of zero to four, as few as zero CourseOffering objects to a maximum of four CourseOffering objects may be linked to one Professor object.

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