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
– Osiris, Commented Nov 24, 2012 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
– Marcello, Commented Nov 24, 2012 at 10:25
That's what composition means. Every instance of Chocolate will have its own FrozenChocolate object, which doesn't seem reasonable. — Osiris
– Osiris, Commented Nov 24, 2012 at 10:26
If thats what it means then why dont you see a composition relationship? — Marcello
– Marcello, Commented Nov 24, 2012 at 10:45

ColinE · Accepted Answer · 2012-11-24 21:59:04Z

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.

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