More than one relationship to a class in a Class Diagram

Question

In a class diagram, is it possible to have two classes with more than one relationship? For example, a generalization relationship and a composition relationship?

For instance,

You can have either a composition relationship or a generalization relationship. A frozen Chocolate is a chocolate. But if you destroy the chocolate class the frozen chocolate class would also be destroyed. which also makes it a composition relationship.

But can you have both on the same diagram, or would you have to stick to one? Which one in this case?

I don't see a composition relationship. Can you declare a `FrozenChocolate frochoc;` in the Chocolate class? — Osiris, Nov 24 '12 at 10:21
If you had to have a frozen Chocolate class. Why wouldn't it not be a composition relationship with the chocolate class? — Marcello, Nov 24 '12 at 10:25
That's what composition means. Every instance of `Chocolate` will have its own `FrozenChocolate` object, which doesn't seem reasonable. — Osiris, Nov 24 '12 at 10:26
If thats what it means then why dont you see a composition relationship? — Marcello, Nov 24 '12 at 10:45

score 1 · Answer 1 · answered Nov 24 '12 at 21:59

This is a generalization relationship, FrozenChocolate is a Chocolate but adds extra properties. It is not a compositions, you cannot say that Chocolate has a FrozenChocolate.

Your argument about destroying Chocolate resulting in FrozenChocolate also being destroyed is invalid. These are not object instances. You cannot say that destroying Animal means that Dog is destroyed.

More than one relationship to a class in a Class Diagram

1 Answers1