burglar_alarm.pl

#!/usr/bin/swipl -f -q

% This is a PROLOG translation of the example in the book
% "Artificial Intelligence: A Modern Approach" by Stuart Russell and Peter Norvig
% Page 512, Figure 14.2

% It uses Ivan Bratko's interpreter for belief networks, figure 15.11,
% from the book "Prolog Programming for Artificial Intelligence"
% Source: http://media.pearsoncmg.com/intl/ema/ema_uk_he_bratko_prolog_3/prolog/ch15/fig15_11.txt
% That program should be renamed fig15_11.pl and put in the same directory to load properly.
% Additionally, if you're using a recent version of SWI Prolog, then
% change the three occurences (on lines 31, 33, 67) of "not X" (or "not Y") in
% fig15_11.pl to "not(X)" (or "not(Y)" respectively). And change "Cond" on line 49
% to an underbar "_" to avoid the "Singleton variables" warning.
:- [fig15_11].

% Setup the belief network...
parent(burglary, alarm).
parent(earthquake, alarm).
parent(alarm, johncalls).
parent(alarm, marycalls).

% Setup probabilities
p(johncalls, [alarm], 0.90).
p(johncalls, [not(alarm)], 0.05).
p(marycalls, [alarm], 0.70).
p(marycalls, [not(alarm)], 0.01).
p(alarm, [burglary, earthquake], 0.95).
p(alarm, [burglary, not(earthquake)], 0.94).
p(alarm, [not(burglary), earthquake], 0.29).
p(alarm, [not(burglary), not(earthquake)], 0.001).
p(burglary, 0.001).
p(earthquake, 0.002).

% Run queries...
:- initialization main.

main :-
prob([johncalls, marycalls, alarm, not(burglary), not(earthquake)], [], P1), % Should be 0.000628
  format('Pr(johncalls, maryCalls, alarm, ~~burglary, ~~earthquake) = ~f (should be 0.000628)~n', [P1]),
  prob(burglary, [johncalls, marycalls], P2), % Should be 0.284172
  format('Pr(burglary|johncalls, marycalls) = ~f (should be 0.284172)~n', [P2]),
  halt.