There is a better than even chance that Lily is a rhino. It is highly unlikely that Sandra dropped the milk. It is improbable that Bernhard is gray. Chances are slight that if 'Lily is a rhino and Sandra dropped the milk' then Julius is yellow. It is probably the case that if 'Lily is a rhino and Bernhard is gray' then John moved to the garden. It is improbable that if either 'Bernhard is gray' or 'Lily is a rhino' but not both then Brian is a swan.
It is highly likely that either 'Brian is a swan' or 'Sandra dropped the milk' but not both.
Chances are slight that either 'Brian is a swan' or 'Sandra dropped the milk' but not both.
It is highly likely that either 'Brian is a swan' or 'Sandra dropped 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
  0.6::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.1::factX:-and(factA,factB).
  0.7::factY:-and(factA,factC).
  0.1::factZ:-xor(factC,factA).

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

  query(conclusion).
  
Either 'Brian is a swan' or 'Sandra dropped the milk' but not both.