We believe that John got the apple. It is unlikely that Greg is a swan. It is likely that Brian is a frog. We believe that if either 'John got the apple' or 'Greg is a swan' but not both then Bernhard is yellow. It is impossible that if 'Greg is a swan and John got the apple' then Julius is a lion. It is probably not the case that if 'Brian is a frog and John got the apple' then Mary left the milk.
There is a better than even chance that 'Julius is a lion and Brian is a frog'.
It is impossible that 'Julius is a lion and Brian is a frog'.
There is a better than even chance that 'Julius is a lion and Brian is a frog'.

  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
  0.75::factA.
  0.2::factB.
  0.7::factC.
  %hop1
  0.75::factX:-xor(factA,factB).
  0.0::factY:-and(factB,factA).
  0.25::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Julius is a lion and Brian is a frog'.