It is probable that Gertrude is a wolf. It is probable that Greg is a rhino. Chances are slight that Bernhard is a swan. It is highly likely that if either 'Bernhard is a swan' or 'Gertrude is a wolf' but not both then Julius is white. Chances are about even that if 'Greg is a rhino' or 'Bernhard is a swan' or both then John went to the garden. Chances are about even that if 'Gertrude is a wolf and Greg is a rhino' then Mary left the apple.
It is almost certain that 'Mary left the apple and Gertrude is a wolf'.
It is probably not the case that 'Mary left the apple and Gertrude is a wolf'.
It is almost certain that 'Mary left the apple and Gertrude is a wolf'.

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

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

  query(conclusion).
  
'Mary left the apple and Gertrude is a wolf'.