Composition Association Relationships

A composition association is a relationship that represents a "whole/part" relationship. It specifies that the lifetime of the "part" is dependent on the lifetime of the "whole." Composition is a strong form of aggregation.

In a composition association, data typically flows in only one direction—from the whole classifier to the part classifier. For example, composition association connects a "Student" class with a "Schedule" class to indicate that if you remove the student, you must also remove the schedule.

A composition association appears as a solid line with a filled diamond at the association end connected to the classifier representing the composite, or "whole."

You can name any association to describe the nature of the relationship between the two classifiers; however, names are typically not needed, especially if you use association end names.

• Association Relationships
• Specifying Kinds of Association Relationships
• Aggregation Association Relationships
• Adding and Modifying Relationships

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