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.