It is certain that Bernhard is yellow. We doubt that Mary dropped the milk. It is unlikely that Lily is a rhino. Chances are slight that if 'Mary dropped the milk' or 'Lily is a rhino' or both then Gertrude is a sheep. It is almost certain that if 'Lily is a rhino and Bernhard is yellow' then Sandra took the apple. There is a better than even chance that if 'Lily is a rhino' or 'Mary dropped the milk' or both then John went to the office.
It is probably the case that either 'John went to the office' or 'Gertrude is a sheep' but not both.
We doubt that either 'John went to the office' or 'Gertrude is a sheep' but not both.
It is probably the case that either 'John went to the office' or 'Gertrude is a sheep' 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.
  0.2::factC.
  %hop1
  0.1::factX:-or(factB,factC).
  0.95::factY:-and(factC,factA).
  0.6::factZ:-or(factC,factB).

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

  query(conclusion).
  
Either 'John went to the office' or 'Gertrude is a sheep' but not both.