From Wikipedia:There are four different types of association: bi-directional,  uni-directional, Aggregation (includes Composition aggregation) and  Reflexive.From what I know:Composition relationship is used for objects that have a has-a relationship to each other. E.g. A car has-an engine.Whereas, aggregation is a weaker form of composition relationship in which the object doesn't take the ownership of another object. E.g. A university department has a teacher.In association relationship, there's no concept of has a being used and the objects association is completely independent and thus, they don't belong to a certain class. E.g. you drive a car.What does it mean that composition and aggregation are a type of association relationships? or do they stand on their own?On some other resources I have read which state that: Composition is a special form of association and Composition is a special case of association and they are described in independent sections of their own and not in a sub-section of association down below it. Therefore, the confusion about how exactly it is type or sub-type of association relationship.
Is composition and aggregation really a type of association relationship?
object oriented;composition;relationships