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Unit 4: Advanced Class Modelling – I

of the class, together with a value for the qualifier, reduces the multiplicity on the other end of Notes
the association.

!

Caution Qualifiers have the same notation as attributes, have no initial values, and must
be attributes of the association or the class on the other end of the association.
The relationships between work products and units of work and their qualifiers are shown in
Figure 4.9. The qualifiers indicate that a work product with the name of a unit of work may
identify a unit of work, and that a unit of work with the name of a work product may identify a
work product. This is to be observed that we have reduced the multiplicity of 0..* shown in
Figure 4.8 to 0..1 in Figure 4.9. The qualifier enables us to do this.

Did u know? As a UML rule, qualifiers are used only with binary associations.

Figure 4.9: Qualifiers for Associations

Source: http://etutorials.org/Programming/Learning+uml/Part+II+Structural+Modeling/
Chapter+3.+Class+and+Object+Diagrams/3.2+Associations+and+Links/

Self Assessment

Fill in the blanks:
6. An ................. is an endpoint of the line drawn for an association, and it connects the
association to a class.
7. A ................. is shown near the end of an association attached to a class.
8. ................. is shown as an arrow attached to an association end pointing toward the class in
question.
9. A ................. is an attribute of an association class that reduces the multiplicity across an
association.
10. A qualifier is a piece of information used as an ................. to find the objects on the other
end of an association.

4.3 N-ary Association

The degree of an association is the number of roles for each link. Associations may be binary,
ternary, or higher degree. Ternary association and a higher degree association takes place in
advanced class modeling.

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