It is improbable that Greg is a lion. We believe that Brian is a swan. There is a better than even chance that Mary went to the garden. Chances are slight that if either 'Greg is a lion' or 'Brian is a swan' but not both then Bernhard is a frog. It is probable that if 'Mary went to the garden and Greg is a lion' then Lily is a rhino. Chances are about even that if either 'Greg is a lion' or 'Brian is a swan' but not both then John left the apple.
There is little chance that either 'Mary went to the garden' or 'Bernhard is a frog' but not both.
There is a better than even chance that either 'Mary went to the garden' or 'Bernhard is a frog' but not both.
There is little chance that either 'Mary went to the garden' or 'Bernhard is a frog' 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
  0.1::factA.
  0.75::factB.
  0.6::factC.
  %hop1
  0.1::factX:-xor(factA,factB).
  0.7::factY:-and(factC,factA).
  0.5::factZ:-xor(factA,factB).

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

  query(conclusion).
  
Either 'Mary went to the garden' or 'Bernhard is a frog' but not both.