Aggregation vs Composition in UML Diagrams

Aggregation and composition are two types of relationships in UML diagrams that define the association between classes or objects.

Aggregation:

Aggregation represents a relationship where one object is a part of or belongs to another object. It is denoted by a diamond shape on the association line.

In aggregation, the child object can exist independently of the parent object. It implies a "has-a" relationship.

Example: A car has an engine. If the car is destroyed, the engine can still exist.

Composition:

Composition represents a stronger form of aggregation where the child object is a part of the parent object. It is denoted by a filled diamond shape on the association line.

In composition, the child object cannot exist independently of the parent object. It implies a "contains-a" relationship.

Example: A house is composed of rooms. If the house is destroyed, the rooms cease to exist.

It is important to differentiate between aggregation and composition in UML diagrams to accurately depict the relationships between objects in a system.