We believe that Greg is a frog. We doubt that Gertrude is a sheep. It is unlikely that Brian is a lion. There is almost no chance that if 'Brian is a lion and Gertrude is a sheep' then Lily is a rhino. It is highly likely that if either 'Gertrude is a sheep' or 'Brian is a lion' but not both then John moved to the office. It is unlikely that if 'Gertrude is a sheep' or 'Greg is a frog' or both then Yann is tired.
It is probably the case that either 'Gertrude is a sheep' or 'Lily is a rhino' but not both.
We doubt that either 'Gertrude is a sheep' or 'Lily is a rhino' but not both.
It is probably the case that either 'Gertrude is a sheep' or 'Lily 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.
  0.2::factB.
  0.2::factC.
  %hop1
  0.02::factX:-and(factC,factB).
  0.9::factY:-xor(factB,factC).
  0.2::factZ:-or(factB,factA).

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

  query(conclusion).
  
Either 'Gertrude is a sheep' or 'Lily is a rhino' but not both.