There is almost no chance that John left the football. It is probably the case that Julius is a frog. It is likely that Brian is a swan. It is impossible that if 'John left the football' or 'Julius is a frog' or both then Greg is a lion. We believe that if either 'Brian is a swan' or 'Julius is a frog' but not both then Bernhard is white. It is almost certain that if either 'John left the football' or 'Brian is a swan' but not both then Mary took the milk.
Chances are about even that 'Brian is a swan and Julius is a frog'.
Chances are about even that 'Brian is a swan and Julius is a frog'.
It is almost certain that 'Brian is a swan and Julius 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
  0.02::factA.
  0.7::factB.
  0.7::factC.
  %hop1
  0.0::factX:-or(factA,factB).
  0.75::factY:-xor(factC,factB).
  0.95::factZ:-xor(factA,factC).

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

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