It is probable that Jessica is a cat. There is a very good chance that Brian is a swan. There is a better than even chance that Bernhard is a rhino. Chances are slight that if either 'Jessica is a cat' or 'Bernhard is a rhino' but not both then Sandra left the apple. There is almost no chance that if either 'Jessica is a cat' or 'Bernhard is a rhino' but not both then Julius is white. There is a very good chance that if 'Jessica is a cat and Bernhard is a rhino' then John put down the milk.
Chances are slight that either 'John put down the milk' or 'Brian is a swan' but not both.
There is a better than even chance that either 'John put down the milk' or 'Brian is a swan' but not both.
Chances are slight that either 'John put down the milk' or 'Brian is a swan' 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
  0.7::factA.
  0.8::factB.
  0.6::factC.
  %hop1
  0.1::factX:-xor(factA,factC).
  0.02::factY:-xor(factA,factC).
  0.8::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'John put down the milk' or 'Brian is a swan' but not both.