There is almost no chance that Winona is a sheep. Chances are about even that Julius is a lion. There is a very good chance that Mary went to the hallway. There is almost no chance that if either 'Julius is a lion' or 'Winona is a sheep' but not both then Greg is a frog. It is highly unlikely that if 'Mary went to the hallway and Julius is a lion' then Brian is a swan. It is almost certain that if 'Mary went to the hallway and Winona is a sheep' then John left the apple.
It is highly unlikely that 'Winona is a sheep' or 'Brian is a swan' or both.
It is highly unlikely that 'Winona is a sheep' or 'Brian is a swan' or both.
It is certain that 'Winona is a sheep' or 'Brian is a swan' 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
  0.02::factA.
  0.5::factB.
  0.8::factC.
  %hop1
  0.02::factX:-xor(factB,factA).
  0.05::factY:-and(factC,factB).
  0.95::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Winona is a sheep' or 'Brian is a swan' or both.