There is a better than even chance that Sandra dropped the milk. It is highly likely that Bernhard is a swan. There is a better than even chance that Greg is a frog. It is highly likely that if either 'Sandra dropped the milk' or 'Greg is a frog' but not both then Brian is yellow. There is a better than even chance that if 'Greg is a frog' or 'Bernhard is a swan' or both then Julius is a rhino. There is a better than even chance that if 'Greg is a frog and Sandra dropped the milk' then John left the apple.
It is highly unlikely that 'Greg is a frog and Bernhard is a swan'.
Chances are about even that 'Greg is a frog and Bernhard is a swan'.
It is highly unlikely that 'Greg is a frog and Bernhard is a swan'.

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

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

  query(conclusion).
  
'Greg is a frog and Bernhard is a swan'.