Chances are slight that Mary left the milk. It is probably the case that Daniel took the apple. There is a better than even chance that Fred moved to the office. Chances are slight that if 'Fred moved to the office and Mary left the milk' then Bernhard is a swan. It is probably not the case that if 'Mary left the milk' or 'Fred moved to the office' or both then Winona is a mouse. There is almost no chance that if 'Mary left the milk' or 'Daniel took the apple' or both then Greg is a frog.
It is improbable that 'Greg is a frog' or 'Daniel took the apple' or both.
It is likely that 'Greg is a frog' or 'Daniel took the apple' or both.
It is improbable that 'Greg is a frog' or 'Daniel took 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
  0.1::factA.
  0.7::factB.
  0.6::factC.
  %hop1
  0.1::factX:-and(factC,factA).
  0.25::factY:-or(factA,factC).
  0.02::factZ:-or(factA,factB).

  %hop2
  conclusion:-or(factZ,factB).

  query(conclusion).
  
'Greg is a frog' or 'Daniel took the apple' or both.