It is unlikely that Bernhard is a swan. It is probably the case that John put down the milk. There is almost no chance that Mary picked up the apple. Chances are about even that if 'Bernhard is a swan and Mary picked up the apple' then Brian is yellow. It is unlikely that if either 'Mary picked up the apple' or 'Bernhard is a swan' but not both then Winona is a cat. It is highly unlikely that if 'John put down the milk' or 'Mary picked up the apple' or both then Lily is a rhino.
It is likely that either 'Lily is a rhino' or 'Mary picked up the apple' but not both.
It is highly unlikely that either 'Lily is a rhino' or 'Mary picked up the apple' but not both.
It is likely that either 'Lily is a rhino' or 'Mary picked up the apple' 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.
  0.7::factB.
  0.02::factC.
  %hop1
  0.5::factX:-and(factA,factC).
  0.2::factY:-xor(factC,factA).
  0.05::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'Lily is a rhino' or 'Mary picked up the apple' but not both.