%%% -*- Mode: Prolog; -*-

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% ProbLog program describing a probabilistic graph
% (running example from ProbLog presentations)
% $Id: graph.pl 4875 2010-10-05 15:28:35Z theo $
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:- use_module(library(problog)).

%%%%
% background knowledge
%%%%
% definition of acyclic path using list of visited nodes
path(X,Y) :- path(X,Y,[X],_).

path(X,X,A,A).
path(X,Y,A,R) :-
	X\==Y,
	edge(X,Z),
	absent(Z,A),
	path(Z,Y,[Z|A],R).

% using directed edges in both directions
edge(X,Y) :- dir_edge(Y,X).
edge(X,Y) :- dir_edge(X,Y).

% checking whether node hasn't been visited before
absent(_,[]).
absent(X,[Y|Z]):-X \= Y, absent(X,Z).

%%%%
% probabilistic facts
%%%%
0.9::dir_edge(1,2).
0.8::dir_edge(2,3).
0.6::dir_edge(3,4).
0.7::dir_edge(1,6).
0.5::dir_edge(2,6).
0.4::dir_edge(6,5).
0.7::dir_edge(5,3).
0.2::dir_edge(5,4).


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% example queries about path(1,4)
%
%%% explanation probability (and facts involved)
%     ?- problog_max(path(1,4),Prob,FactsUsed).
%  FactsUsed = [dir_edge(1,2),dir_edge(2,3),dir_edge(3,4)],
%  Prob = 0.432 ?
%  yes
%%% success probability
%     ?- problog_exact(path(1,4),Prob,Status).
%  8 proofs
%  Prob = 0.53864,
%  Status = ok ?
%  yes
%%% lower bound using 4 best proofs
%     ?- problog_kbest(path(1,4),4,Prob,Status).
%  4 proofs
%  Prob = 0.517344,
%  Status = ok ?
%  yes
%%% approximation using monte carlo, to reach 95%-confidence interval width 0.01
%     ?- problog_montecarlo(path(1,4),0.01,Prob).
%  Prob = 0.537525 ?
%  yes
%%% upper and lower bound using iterative deepening, final interval width 0.01
%    ?- problog_delta(path(1,4),0.01,Bound_low,Bound_up,Status).
%  Bound_low = 0.5354096,
%  Bound_up = 0.53864,
%  Status = ok ?
%  yes
%%% upper and lower bound obtained cutting the sld tree at probability 0.1 for each branch
%     ?- problog_threshold(path(1,4),0.1,Bound_low,Bound_up,Status).
%  4 proofs
%  Bound_low = 0.517344,
%  Bound_up = 0.563728,
%  Status = ok ?
%  yes
%%% lower bound obtained cutting the sld tree at probability 0.2 for each branch
%     ?- problog_low(path(1,4),0.2,Bound_low,Status).
%  1 proofs
%  Bound_low = 0.432,
%  Status = ok ?
%  yes
%
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