The third type of relationship that we saw, is
Generalization. Generalization is a relationship, between a general class,
which we normally call super-class and the more specific
class, a class the refines the super-class and that
we normally call sub-class. It's also known as a
kind of or is a relationship because we can
say that the subclass is a super class and
it's expressed with a solid line with a big arrow
head at the end. So let's see an example of
that. In this case I'm going to indicate. Two of this kind
of relationships. The first one involving the RegistrationUser and
a student. And the second one, a RegistrationUser and the
professor. So, basically what we're showing here is a
typical case in which the registration user is a more general
concept then the Student and the Professor. So both the student
and the professor are RegistrationUsers. So there is a relationship,
the Professor is a registration user and the Student is a RegistrationUser.
And therefore we can indicate that using
the generalization relationship in our class diagram.