It is certain that John discarded the milk. It is unlikely that Mary left the football. We believe that Brian is a frog. It is unlikely that if 'Brian is a frog' or 'John discarded the milk' or both then Bernhard is a rhino. It is probable that if either 'Mary left the football' or 'John discarded the milk' but not both then Lily is a swan. We doubt that if 'Brian is a frog' or 'Mary left the football' or both then Julius is yellow.
There is a very good chance that either 'Bernhard is a rhino' or 'John discarded the milk' but not both.
There is a very good chance that either 'Bernhard is a rhino' or 'John discarded the milk' but not both.
There is almost no chance that either 'Bernhard is a rhino' or 'John discarded 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
  1.0::factA.
  0.2::factB.
  0.75::factC.
  %hop1
  0.2::factX:-or(factC,factA).
  0.7::factY:-xor(factB,factA).
  0.2::factZ:-or(factC,factB).

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

  query(conclusion).
  
Either 'Bernhard is a rhino' or 'John discarded the milk' but not both.