There is a better than even chance that John dropped the apple. Chances are slight that Greg is a frog. It is probably not the case that Mary went to the office. It is unlikely that if either 'Mary went to the office' or 'Greg is a frog' but not both then Brian is a rhino. There is little chance that if either 'John dropped the apple' or 'Greg is a frog' but not both then Julius is gray. We believe that if 'John dropped the apple' or 'Greg is a frog' or both then Bernhard is green.
There is a very good chance that 'Mary went to the office' or 'Julius is gray' or both.
It is probably not the case that 'Mary went to the office' or 'Julius is gray' or both.
There is a very good chance that 'Mary went to the office' or 'Julius is gray' 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
  0.6::factA.
  0.1::factB.
  0.25::factC.
  %hop1
  0.2::factX:-xor(factC,factB).
  0.1::factY:-xor(factA,factB).
  0.75::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Mary went to the office' or 'Julius is gray' or both.