It is improbable that Mary went to the garden. It is almost certain that Greg is a swan. It is almost certain that John discarded the apple. It is likely that if 'Greg is a swan and Mary went to the garden' then Bernhard is yellow. It is probably the case that if 'John discarded the apple and Greg is a swan' then Brian is a lion. There is a better than even chance that if 'Mary went to the garden and Greg is a swan' then Julius is a rhino.
It is probable that either 'John discarded the apple' or 'Brian is a lion' but not both.
It is probably not the case that either 'John discarded the apple' or 'Brian is a lion' but not both.
It is probable that either 'John discarded the apple' or 'Brian is a lion' 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.
  0.95::factB.
  0.95::factC.
  %hop1
  0.7::factX:-and(factB,factA).
  0.7::factY:-and(factC,factB).
  0.6::factZ:-and(factA,factB).

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

  query(conclusion).
  
Either 'John discarded the apple' or 'Brian is a lion' but not both.