We believe that Daniel left the football. It is certain that Jessica is a cat. It is unlikely that Lily is a swan. There is little chance that if 'Jessica is a cat and Lily is a swan' then Brian is a rhino. There is almost no chance that if either 'Daniel left the football' or 'Lily is a swan' but not both then Greg is white. There is little chance that if 'Lily is a swan' or 'Jessica is a cat' or both then Mary grabbed the milk.
We believe that either 'Daniel left the football' or 'Brian is a rhino' but not both.
We believe that either 'Daniel left the football' or 'Brian is a rhino' but not both.
It is probably not the case that either 'Daniel left the football' or 'Brian is a rhino' 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.
  1.0::factB.
  0.2::factC.
  %hop1
  0.1::factX:-and(factB,factC).
  0.02::factY:-xor(factA,factC).
  0.1::factZ:-or(factC,factB).

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

  query(conclusion).
  
Either 'Daniel left the football' or 'Brian is a rhino' but not both.