We believe that Gertrude is a cat. It is almost certain that Greg is a swan. It is probably not the case that Mary took the milk. It is likely that if 'Mary took the milk and Greg is a swan' then Jessica is a sheep. It is likely that if 'Mary took the milk' or 'Gertrude is a cat' or both then Lily is a lion. It is highly likely that if either 'Mary took the milk' or 'Greg is a swan' but not both then Emily is a sheep.
There is a better than even chance that either 'Gertrude is a cat' or 'Mary took the milk' but not both.
There is a better than even chance that either 'Gertrude is a cat' or 'Mary took the milk' but not both.
It is highly unlikely that either 'Gertrude is a cat' or 'Mary took 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
  0.75::factA.
  0.95::factB.
  0.25::factC.
  %hop1
  0.7::factX:-and(factC,factB).
  0.7::factY:-or(factC,factA).
  0.9::factZ:-xor(factC,factB).

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

  query(conclusion).
  
Either 'Gertrude is a cat' or 'Mary took the milk' but not both.