We believe that Mary dropped the apple. There is little chance that Winona is a sheep. We believe that Julius is a frog. It is probably not the case that if either 'Julius is a frog' or 'Mary dropped the apple' but not both then Lily is a lion. It is probable that if 'Mary dropped the apple' or 'Julius is a frog' or both then John discarded the milk. It is likely that if 'Julius is a frog and Winona is a sheep' then Greg is a swan.
There is little chance that 'John discarded the milk' or 'Mary dropped the apple' or both.
It is highly likely that 'John discarded the milk' or 'Mary dropped the apple' or both.
There is little chance that 'John discarded the milk' or 'Mary 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
  0.75::factA.
  0.1::factB.
  0.75::factC.
  %hop1
  0.25::factX:-xor(factC,factA).
  0.7::factY:-or(factA,factC).
  0.7::factZ:-and(factC,factB).

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

  query(conclusion).
  
'John discarded the milk' or 'Mary dropped the apple' or both.