It is likely that Daniel left the milk. It is almost certain that Brian is yellow. It is highly unlikely that Greg is white. It is unlikely that if either 'Greg is white' or 'Daniel left the milk' but not both then Bernhard is a frog. Chances are slight that if 'Brian is yellow' or 'Greg is white' or both then Mary picked up the apple. There is a better than even chance that if either 'Brian is yellow' or 'Daniel left the milk' but not both then John went to the bedroom.
It is probable that 'Mary picked up the apple' or 'Bernhard is a frog' or both.
We doubt that 'Mary picked up the apple' or 'Bernhard is a frog' or both.
It is probable that 'Mary picked up the apple' or 'Bernhard is a frog' 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.
  0.95::factB.
  0.05::factC.
  %hop1
  0.2::factX:-xor(factC,factA).
  0.1::factY:-or(factB,factC).
  0.6::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Mary picked up the apple' or 'Bernhard is a frog' or both.