A knowledge base for identifying faults in an electric network

Source: PROLOG programming for artificial intelligence, 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7.

Program source code: electrical_network_kb.pl

% Figure 16.3  A knowledge base for identifying faults in an electric
% network such as the one in Figure 16.2.
 
:-  op( 200, xfy, [:, ::]).
:-  op( 185, fx, if).
:-  op( 190, xfx, then).
:-  op( 180, xfy, or).
:-  op( 160, xfy, and).
:-  op( 140, fx, not).
 
% A small knowledge base for locating faults in an electric network
 
%  If a device is on and not working and its fuse is intact
%  then the device is broken.
 
broken_rule ::
		if
			on(Device)  and
			device( Device)  and
			(not working(Device))  and
			connected( Device, Fuse)  and
	                proved( intact( Fuse))
		then
                        proved( broken( Device)).
 
%  If a unit is working
%  then its fuse is OK.
 
fuse_ok_rule ::
		if
			connected( Device, Fuse)  and
			working( Device)
		then
                        proved( intact( Fuse)).
 
 
%  If two different devices are connected to a fuse and
%  are both on and not working then the fuse has failed.
%  NOTE: This assumes that at most one device is broken!
 
fused_rule ::
		if
			connected( Device1, Fuse)  and
			on( Device1)  and
			(not working( Device1))  and
			samefuse( Device2, Device1)  and
			on( Device2)  and
			(not working( Device2))
		then
                        proved( failed( Fuse)).
 
 
same_fuse_rule ::
		if
			connected( Device1, Fuse)  and
			connected( Device2, Fuse)  and
			different( Device1, Device2)
 		then
			samefuse( Device1, Device2).
 
device_on_rule ::
        if
              working( Device)
        then
              on( Device).
 
 
fact :: different( X, Y)   :-   not (X = Y).
 
fact :: device( heater).
fact :: device( light1).
fact :: device( light2).
fact :: device( light3).
fact :: device( light4).
 
fact :: connected( light1, fuse1).
fact :: connected( light2, fuse1).
fact :: connected( heater, fuse1).
fact :: connected( light3, fuse2).
fact :: connected( light4, fuse2).
 
 
askable( on(D), on('Device')).
 
askable( working(D), working('Device')).