It is probable that Fred went to the garden. It is highly likely that Lily is a frog. We believe that Bernhard is yellow. There is almost no chance that if 'Fred went to the garden and Lily is a frog' then Daniel took the milk. It is unlikely that if 'Lily is a frog and Bernhard is yellow' then Mary dropped the milk. It is unlikely that if 'Bernhard is yellow' or 'Fred went to the garden' or both then Julius is a swan.
We doubt that 'Mary dropped the milk' or 'Fred went to the garden' or both.
We believe that 'Mary dropped the milk' or 'Fred went to the garden' or both.
We doubt that 'Mary dropped the milk' or 'Fred went to the garden' 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.
  0.9::factB.
  0.75::factC.
  %hop1
  0.02::factX:-and(factA,factB).
  0.2::factY:-and(factB,factC).
  0.2::factZ:-or(factC,factA).

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

  query(conclusion).
  
'Mary dropped the milk' or 'Fred went to the garden' or both.