Dear Richard,

Oops again. :-(

[Double oops. I sent this to myself instead of the list.]

I wrote:

> If ClassA inherits ClassB's behavior, but adds other
behavior, ClassB is
> a subclass of ClassA, but can simulate ClassA simply by
not using the
> added behavior, whereas ClassA cannot simulate ClassB
without it.

That's the second time tonight I have said the opposite of
what I meant.
I must be getting sleepy. Sorry.

How about this?

If ClassB inherits ClassA's behavior, but adds other
behavior, ClassB is
a subclass of ClassA, but can simulate ClassA simply by not
using the
added behavior, whereas ClassA cannot simulate ClassB
without it.

Good night.

Bill