5. In what ways can aggregation be distinguished from composition for a whole-part relationship?
Aggregation and composition are both types of relationships that indicate a whole-part relationship between objects. However, there are some key differences that can help distinguish between the two:
1. Existence dependency: In composition, the part objects cannot exist without the whole object. This means that when the whole object is destroyed, the part objects are also destroyed. In contrast, in aggregation, the part objects can exist independently of the whole object.
2. Typeness: In composition, the whole object usually owns the part objects and is responsible for their creation and destruction. In aggregation, the part objects may not necessarily be owned by the whole object and can exist outside of it.
3. Lifecycle: In composition, the lifecycle of the part objects is tightly coupled with the lifecycle of the whole object. In aggregation, the lifecycle of the part objects is independent of the lifecycle of the whole object.
4. Navigability: In aggregation, the part objects can be accessed directly by external objects, as they exist independently. In composition, the part objects are typically encapsulated within the whole object and cannot be directly accessed from outside.
Overall, the main difference between aggregation and composition lies in the strength and dependency of the relationship between the whole and the part objects. Aggregation represents a weaker relationship where the part objects can exist independently, while composition represents a stronger relationship where the part objects are tightly coupled with the whole object.