There is almost no chance that Mary took the football. It is highly likely that Julius is a swan. It is probably not the case that John went to the garden. There is almost no chance that if either 'John went to the garden' or 'Julius is a swan' but not both then Brian is a rhino. There is a very good chance that if 'Mary took the football and John went to the garden' then Greg is a frog. It is unlikely that if either 'Mary took the football' or 'John went to the garden' but not both then Daniel dropped the milk.
It is certain that 'Greg is a frog and Daniel dropped the milk'.
It is impossible that 'Greg is a frog and Daniel dropped the milk'.
It is certain that 'Greg is a frog and Daniel dropped the milk'.

  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.
  0.9::factB.
  0.25::factC.
  %hop1
  0.02::factX:-xor(factC,factB).
  0.8::factY:-and(factA,factC).
  0.2::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Greg is a frog and Daniel dropped the milk'.