Jim,

>The points I am making are OO Hueristics, not rules or laws. That is they represent best practises which will prevent certain problems. They are not absolutes in any way.

Point taken, however the fowolling sentence:

>You never subclass a container that has anything in it.

should be:

Avoid subclassing a container that has anything in it.

Your reply towards ko, gave the impression that subclassing a container with something in it is a bad practise. In any way, I think it's not.

Walter,