posted 19 years ago
Aggregation is the part-of relationship. It is like Car has Wheel (s) as its part.
So if you consider two objects Car and Wheel, then we can say Car aggregates Wheel (s). Also the Wheel object can also be a part of another object say Lorry.
So the part (Wheel) is can be binded to n whole (Car, Lorry) objects and the "part" can exist with out the "Whole".
Composition is a kind of association used to model the whole-part relationships between things. In this case the "part" cannot exist without the "whole" usually the "parts" are expected to live and die with the "whole". Any deletion of the "whole" is considered to cascade to the "parts".