Chances are slight that Bernhard is a rhino. It is highly likely that Bill moved to the office. It is highly likely that Lily is a frog. It is impossible that if 'Bill moved to the office and Bernhard is a rhino' then Brian is a swan. Chances are about even that if 'Lily is a frog' or 'Bernhard is a rhino' or both then John dropped the apple. There is a better than even chance that if 'Lily is a frog' or 'Bill moved to the office' or both then Julius is white.
There is a very good chance that either 'Bernhard is a rhino' or 'Bill moved to the office' but not both.
There is a very good chance that either 'Bernhard is a rhino' or 'Bill moved to the office' but not both.
It is unlikely that either 'Bernhard is a rhino' or 'Bill moved to the office' 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
  0.1::factA.
  0.9::factB.
  0.9::factC.
  %hop1
  0.0::factX:-and(factB,factA).
  0.5::factY:-or(factC,factA).
  0.6::factZ:-or(factC,factB).

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

  query(conclusion).
  
Either 'Bernhard is a rhino' or 'Bill moved to the office' but not both.