It is probably the case that Greg is white. We believe that Jessica is a mouse. There is little chance that Mary left the football. There is almost no chance that if either 'Jessica is a mouse' or 'Greg is white' but not both then Julius is a swan. It is certain that if either 'Mary left the football' or 'Greg is white' but not both then Winona is a sheep. It is unlikely that if either 'Greg is white' or 'Jessica is a mouse' but not both then John dropped the apple.
It is probably not the case that 'Winona is a sheep' or 'John dropped the apple' or both.
It is likely that 'Winona is a sheep' or 'John dropped the apple' or both.
It is probably not the case that 'Winona is a sheep' or 'John dropped the apple' or both.

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

  %hop2
  conclusion:-or(factY,factZ).

  query(conclusion).
  
'Winona is a sheep' or 'John dropped the apple' or both.