It is likely that Fred went to the garden. There is little chance that Julius is a rhino. It is improbable that Greg is yellow. There is almost no chance that if 'Julius is a rhino' or 'Greg is yellow' or both then Mary dropped the apple. There is almost no chance that if either 'Greg is yellow' or 'Fred went to the garden' but not both then Winona is a wolf. It is improbable that if either 'Fred went to the garden' or 'Julius is a rhino' but not both then Lily is a swan.
We doubt that either 'Lily is a swan' or 'Julius is a rhino' but not both.
We doubt that either 'Lily is a swan' or 'Julius is a rhino' but not both.
It is probably the case that either 'Lily is a swan' or 'Julius is a rhino' 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.
  0.1::factB.
  0.1::factC.
  %hop1
  0.02::factX:-or(factB,factC).
  0.02::factY:-xor(factC,factA).
  0.1::factZ:-xor(factA,factB).

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

  query(conclusion).
  
Either 'Lily is a swan' or 'Julius is a rhino' but not both.