Let’s say I have BaseA and BaseB classes. BaseB can have to several references of BaseA instances. Now, we have two other classes, DerivedA and DerivedB that respectively inherit from BaseA and BaseB.

How can I show in such a diagram that DerivedB should only store instances of DerivedA and not instances of BaseA? It seemed pretty simple before I tried to draw it, but now I’m confused. One obvious answer would be “redesign your code”; if there is no alternative, I will probably try to do so.