There are different kinds of relationships: Dependencies, Generalization, and
Association. Dependencies are relations ships between two entities that that a
change in specification of one thing may affect another thing. Most commonly it is
used to show that one class uses another class as an argument in the signature of
the operation. Generalization is relationships specified in the class subclass
scenario, it is shown when one entity inherits from other. Associations are
structural relationships that are: a room has walls, Person works for a company.
Aggregation is a type of association where there is a has a relation ship, That is a
room has walls, ño if there are two classes room and walls then the relation ship
is called a association and further defined as an aggregation.