It is likely that Mary got the apple. There is a better than even chance that Sandra left the football. There is a better than even chance that Greg is a frog. There is a very good chance that if 'Greg is a frog' or 'Sandra left the football' or both then Gertrude is a sheep. It is certain that if either 'Greg is a frog' or 'Sandra left the football' but not both then John went to the kitchen. It is highly likely that if 'Mary got the apple and Greg is a frog' then Bernhard is a swan.
It is probably not the case that either 'Gertrude is a sheep' or 'Sandra left the football' but not both.
It is probably not the case that either 'Gertrude is a sheep' or 'Sandra left the football' but not both.
It is highly likely that either 'Gertrude is a sheep' or 'Sandra left the football' 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.
  0.6::factB.
  0.6::factC.
  %hop1
  0.8::factX:-or(factC,factB).
  1.0::factY:-xor(factC,factB).
  0.9::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Gertrude is a sheep' or 'Sandra left the football' but not both.