% H4 / ECAL diagnosis (simplified)

connected(h4, crystal).
connected(crystal, apd).
connected(testpulse_injector, apd).
connected(apd, readout).

good_path(X,Y) :- not bad(X), not bad(Y), connected(X, Y).
good_path(X,Z) :- good_path(X,Y), good_path(Y, Z).

bad(crystal) v bad(apd). 

testpulse_readout_ok :- good_path(testpulse_injector, readout).
beam_readout_ok :- good_path(h4, readout).

:- not beam_readout_ok.
:- not testpulse_readout_ok.