It is probably the case that Bernhard is gray. We believe that Fred dropped the apple. It is impossible that John went to the bedroom. It is almost certain that if 'Bernhard is gray and Fred dropped the apple' then Mary took the milk. It is probable that if 'Fred dropped the apple and John went to the bedroom' then Greg is a swan. It is highly likely that if 'Bernhard is gray and John went to the bedroom' then Brian is yellow.
It is impossible that 'Fred dropped the apple and John went to the bedroom'.
It is impossible that 'Fred dropped the apple and John went to the bedroom'.
We believe that 'Fred dropped the apple and John went to the bedroom'.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  0.7::factA.
  0.75::factB.
  0.0::factC.
  %hop1
  0.95::factX:-and(factA,factB).
  0.7::factY:-and(factB,factC).
  0.9::factZ:-and(factA,factC).

  %hop2
  conclusion:-and(factB,factC).

  query(conclusion).
  
'Fred dropped the apple and John went to the bedroom'.