Chances are slight that Sandra left the milk. Chances are slight that John discarded the apple. There is a very good chance that Brian is a swan. It is probably the case that if 'John discarded the apple and Sandra left the milk' then Bernhard is a frog. Chances are slight that if 'Brian is a swan' or 'John discarded the apple' or both then Mary went to the office. It is highly likely that if either 'Sandra left the milk' or 'Brian is a swan' but not both then Emily is a wolf.
There is a very good chance that either 'John discarded the apple' or 'Sandra left the milk' but not both.
It is unlikely that either 'John discarded the apple' or 'Sandra left the milk' but not both.
There is a very good chance that either 'John discarded the apple' or 'Sandra left the milk' 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.
  0.1::factB.
  0.8::factC.
  %hop1
  0.7::factX:-and(factB,factA).
  0.1::factY:-or(factC,factB).
  0.9::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'John discarded the apple' or 'Sandra left the milk' but not both.