Analyzing Association Traversal
Till now, we have supposed that associations are bi-directional. But in the case of traversal, it is in only one direction in any application, implementation becomes easier.
Though, for finding unidirectional associations we require to be extra cautious, as any new operation added later can be required to traverse association in the opposite direction also. The bi-directional association makes expansion or modification easier.
To change our decision of implementation strategy with least effort, we should hide implementation, using access operations to traverse and update association.