It is certain that Sandra left the milk. It is certain that Bernhard is gray. It is unlikely that John picked up the apple. There is little chance that if 'Sandra left the milk and John picked up the apple' then Greg is a frog. It is highly likely that if either 'John picked up the apple' or 'Bernhard is gray' but not both then Brian is green. We doubt that if 'John picked up the apple' or 'Bernhard is gray' or both then Mary went to the bedroom.
It is highly unlikely that 'Bernhard is gray and Sandra left the milk'.
It is certain that 'Bernhard is gray and Sandra left the milk'.
It is highly unlikely that 'Bernhard is gray and Sandra left the milk'.

  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
  1.0::factA.
  1.0::factB.
  0.2::factC.
  %hop1
  0.1::factX:-and(factA,factC).
  0.9::factY:-xor(factC,factB).
  0.2::factZ:-or(factC,factB).

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

  query(conclusion).
  
'Bernhard is gray and Sandra left the milk'.