It is unlikely that Sandra dropped the apple. We doubt that Fred is in the cinema. It is impossible that Bill moved to the office. We believe that if either 'Sandra dropped the apple' or 'Bill moved to the office' but not both then John got the milk. Chances are slight that if either 'Sandra dropped the apple' or 'Fred is in the cinema' but not both then Mary went to the garden. Chances are about even that if either 'Bill moved to the office' or 'Fred is in the cinema' but not both then Julius is white.
It is probably not the case that either 'Fred is in the cinema' or 'John got the milk' but not both.
It is probably not the case that either 'Fred is in the cinema' or 'John got the milk' but not both.
It is highly likely that either 'Fred is in the cinema' or 'John got the milk' 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
  0.2::factA.
  0.2::factB.
  0.0::factC.
  %hop1
  0.75::factX:-xor(factA,factC).
  0.1::factY:-xor(factA,factB).
  0.5::factZ:-xor(factC,factB).

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

  query(conclusion).
  
Either 'Fred is in the cinema' or 'John got the milk' but not both.