It is certain that Mary went to the bedroom. It is probably the case that Jessica is a sheep. It is highly unlikely that Bernhard is a rhino. It is likely that if either 'Bernhard is a rhino' or 'Mary went to the bedroom' but not both then Brian is a frog. It is probably not the case that if 'Bernhard is a rhino and Mary went to the bedroom' then Julius is a swan. Chances are slight that if 'Jessica is a sheep' or 'Bernhard is a rhino' or both then John took the apple.
It is likely that either 'Brian is a frog' or 'Julius is a swan' but not both.
It is likely that either 'Brian is a frog' or 'Julius is a swan' but not both.
There is little chance that either 'Brian is a frog' or 'Julius 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
  1.0::factA.
  0.7::factB.
  0.05::factC.
  %hop1
  0.7::factX:-xor(factC,factA).
  0.25::factY:-and(factC,factA).
  0.1::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'Brian is a frog' or 'Julius is a swan' but not both.