Unified Modeling Language (UML) is a visual language used in software design. It’s just like preparing the design model before constructing the building. In UML, we use three key concepts to define how classes and objects relate to each other: association, aggregation, and composition.
- Association: It represents a basic connection between classes, showing that they are related in some way. Think of it as a simple link.
Example: Consider a “Teacher” class and a “Student” class. An association between these classes represents that a teacher can teach many students, and a student can be taught by many teachers.
2. Aggregation: This is a “has-a” relationship where one class contains another, but the contained class can exist independently.
Example: In a class diagram, consider a “Car” class and a “Wheel” class. The aggregation relationship indicates that a car has wheels, but wheels can exist independently of a car.
3. Composition: It’s a stronger “has-a” relationship, indicating that the parts are essential components of the whole, and they cannot exist independently.
Example: Consider a “House” class and a “Room” class. The composition relationship indicates that a room is an integral part of a house, and when the house is destroyed, the rooms are destroyed as well.
These concepts help us describe relationships in a clear and precise manner when designing software systems using UML diagrams.