We doubt that Brian is white. Chances are about even that Daniel got the football. It is probably not the case that Bernhard is a rhino. It is improbable that if 'Bernhard is a rhino and Brian is white' then Greg is a frog. It is impossible that if 'Brian is white' or 'Daniel got the football' or both then Jessica is a sheep. There is almost no chance that if 'Daniel got the football and Bernhard is a rhino' then Gertrude is a mouse.
It is certain that either 'Daniel got the football' or 'Brian is white' but not both.
Chances are about even that either 'Daniel got the football' or 'Brian is white' but not both.
It is certain that either 'Daniel got the football' or 'Brian is white' 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
  0.2::factA.
  0.5::factB.
  0.25::factC.
  %hop1
  0.1::factX:-and(factC,factA).
  0.0::factY:-or(factA,factB).
  0.02::factZ:-and(factB,factC).

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

  query(conclusion).
  
Either 'Daniel got the football' or 'Brian is white' but not both.