% -*-Prolog-*- %% a simple Pfc example - the standard circuit diagnosis problem. %% %% Tim Finin, finin@prc.unisys.com, 9/29/88 % Devices behave as intended unless they are faulty. isa(X,Class), ~faulty(X) => behave(X,Class). % a wire equates the values at each end. wire(T1,T2) => (pv(T1,V) <=> pv(T2,V)), (ov(T1,V) <=> ov(T2,V)). pv(T,X), ~ov(T,_), ~pv(T,Y)/{Y\==X} => v(T,X). ov(T,X) => v(T,X). % It is a conflict if a terminal has two different values. v(T,V1), v(T,V2)/(\+V1=:=V2) => conflict(two_values(T,V1,V2)). % assume an observation is true. observed(P), ~false_observation(P) => P. % a conflict triggers a Prolog action to resolve it. % conflict(C) => {resolveConflict(C)}. % this isn't written yet. resolveConflict(C) :- format("~NHalting with conflict ~w", [C]), pfcHalt. % an adder's behaviour behave(X,adder) => (v(in(1,X),I1), v(in(2,X),I2) => {O is I1+I2}, pv(out(X),O)), (v(in(1,X),I1), v(out(X),O), {I2 is O-I1} => pv(in(2,X),I2)), (v(in(2,X),I2), v(out(X),O), {I1 is O-I2} => pv(in(1,X),I1)). % a multiplier's behaviour. behave(X,multiplier) => (v(in(1,X),I1), v(in(2,X),I2) => {O is I1*I2}, pv(out(X),O)), ( v(in(1,X),I1), v(out(X),O), {I2 is O/I1} => pv(in(2,X),I2)), (v(in(2,X),I2), v(out(X),O), {I1 is O/I2} => pv(in(1,X),I1) ). % meta rules to schedule inferencing. % resolve conflicts asap pfcSelect(conflict(X)) :- pfcQueue(conflict(X)). %% ***** here is a particular test case. ***** % here is a particular circuit - a gizmo. isa(X,gizmo) => isa(m1(X),multiplier), isa(m2(X),multiplier), isa(m3(X),multiplier), isa(a1(X),adder), isa(a2(X),adder), wire(out(m1(X)),in(1,a1(X))), wire(out(m2(X)),in(2,a1(X))), wire(out(m2(X)),in(1,a2(X))), wire(out(m3(X)),in(2,a2(X))). %% here is a diagnostic problem for a gizmo. test(X) :- add([isa(X,gizmo), ov(in(1,m1(X)),3.0), ov(in(2,m1(X)),2.0), ov(in(1,m2(X)),3.0), ov(in(2,m2(X)),2.0), ov(in(1,m3(X)),2.0), ov(in(2,m3(X)),3.0), ov(out(a1(X)),10.0), ov(out(a2(X)),12.0)]). cs1(L) :- bagof((X,PV,OV), (pv(X,PV),ov(X,OV),PV\==OV), L). cs2(L) :- bagof((X,PV,PV2), (pv(X,PV),pv(X,PV2),PV\==PV2), L). inspect(T) :- bag(V,v(T,V),Vs), bag(PV,pv(T,PV),PVs), bag(OV,ov(T,OV),OVs), format("~nValues for terminal ~w:",[T]), format("~n observed: ~w",[OVs]), format("~n predicted: ~w",[PVs]), format("~n values: ~w",[Vs]). bag(Template,Goal,List) :- bagof(Template,Goal,List) -> true ; List=[].