Association, Aggregation and Composition

Associations indicate that the two classes have a relationship as discussed above. Composition and aggregation indicate something more about the relationship:Composition indicates that one class belongs to the other. A polygon is made up of several points. If the polygon is destroyed, so are the points.Aggregation is similar to composition, but is a less rigorous way of grouping things. An order is made up of several products, but a product continues to exist even if the order is destroyed