:- dynamic(not/1).

:- include(library(pfc_header_3_0)).

:- dynamic(fly/1).

% -*-Prolog-*-
% here is an example which defines default facts and rules.  Will it work?

(default(P)/pfcAtom(P))  ==>  (~not(P) ==> P).

default((P ==> Q))/pfcAtom(Q) ==> (P, ~not(Q) ==> Q).

% birds fly by default.
==> default((bird(X) ==> fly(X))).

% here's one way to do an genlz hierarchy.
% genlz = subclass.

genlz(C1,C2) ==>
  {P1 =.. [C1,X],
    P2 =.. [C2,X],
    dynamic(C1/1),dynamic(C2/1)},
  (P1 ==> P2).

==> genlz(canary,bird).
==> genlz(penguin,bird).

% penguins do not fly.
penguin(X) ==> not(fly(X)).


% chilly is a penguin.
==> penguin(chilly).

% tweety is a canary.
==> canary(tweety).