There is a very good chance that Brian is yellow. It is probably not the case that Daniel took the apple. It is unlikely that Greg is a frog. It is highly unlikely that if 'Daniel took the apple' or 'Greg is a frog' or both then Bernhard is a swan. It is certain that if 'Greg is a frog' or 'Daniel took the apple' or both then John went to the kitchen. It is improbable that if 'Brian is yellow and Greg is a frog' then Mary picked up the milk.
Chances are about even that 'Greg is a frog' or 'John went to the kitchen' or both.
Chances are about even that 'Greg is a frog' or 'John went to the kitchen' or both.
It is highly unlikely that 'Greg is a frog' or 'John went to the kitchen' 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
  0.8::factA.
  0.25::factB.
  0.2::factC.
  %hop1
  0.05::factX:-or(factB,factC).
  1.0::factY:-or(factC,factB).
  0.1::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Greg is a frog' or 'John went to the kitchen' or both.