Thanks. I really appreciate your responses.
San:
a) The way I am visualizing my problem it is sufficient to know that classes B,C,D,E are of type 'Parent' class. I don't have to deal with specific subclasses. Since class A is holding just a Collection<Parent> I am only representing the relation between class A and 'Parent' as 1-to-many.
b) I want class A to treat classes B,C,D,E the same hence E extending 'Parent'. You can think of the class 'Parent' as the Component class of the Composite Design
pattern with B,C,E being the leaves. Class D is the Composite of the pattern and is composed of class E.
Antoni:
I thought such modifications were fine
especially because something similar has been done in the
SCEA Study Guide by Cade and Sheil.
The business domain shows AvailabilityNotice as associated with Concrete, Wood and Steel classes. This was modified by introducing a parent class AvailabilityItem to Concrete, Wood and Steel classes and showing the association between AvailabilityNotice and AvailabilityItem.
But I'll seriously consider doing what you have suggested.
Thanks again,