Ada 2005 OOP : newbie questions

[Bill Findlay <news@findlayw.plus.com>]

I have a package P that declares

   type R is new Limited_Controlled with private;

The private extension of R contains a number of fields that I want to be
common to future derived types S, T, etc; P declares a number of primitive
operation signatures of R that I want S, T, etc, to override; and there are
some operations on R'Class in P as well.

1. Can I prevent objects of type P.R from being declared,
   while allowing objects of types S, T, etc?

2. Can I prevent a useless primitive of P.R, say P.Op from being called?
   At the moment the body of P.Op raises an exception, but I would much
   prefer to have a compile-time check (of course).

I feel sure that there is a general way of dealing with such issues,
but at the moment I can't seem to see the wood for the trees.

-- 
Bill Findlay
with blueyonder.co.uk;
use  surname & forename;