It is improbable that Mary dropped the apple. We believe that Julius is white. It is highly likely that Brian is a lion. Chances are about even that if either 'Julius is white' or 'Brian is a lion' but not both then Bernhard is gray. It is certain that if 'Mary dropped the apple' or 'Brian is a lion' or both then Winona is a wolf. It is probably the case that if 'Julius is white and Mary dropped the apple' then Sumit is bored.
There is a very good chance that either 'Sumit is bored' or 'Bernhard is gray' but not both.
We doubt that either 'Sumit is bored' or 'Bernhard is gray' but not both.
There is a very good chance that either 'Sumit is bored' or 'Bernhard is gray' but not 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.
  0.75::factB.
  0.9::factC.
  %hop1
  0.5::factX:-xor(factB,factC).
  1.0::factY:-or(factA,factC).
  0.7::factZ:-and(factB,factA).

  %hop2
  conclusion:-xor(factZ,factX).

  query(conclusion).
  
Either 'Sumit is bored' or 'Bernhard is gray' but not both.