It is highly unlikely that Winona is a wolf. It is certain that Emily is a sheep. It is probable that Fred moved to the office. It is highly likely that if 'Fred moved to the office' or 'Emily is a sheep' or both then Lily is a frog. We believe that if either 'Emily is a sheep' or 'Winona is a wolf' but not both then Mary dropped the milk. It is probably the case that if either 'Winona is a wolf' or 'Emily is a sheep' but not both then Brian is a swan.
It is impossible that either 'Brian is a swan' or 'Winona is a wolf' but not both.
It is probably the case that either 'Brian is a swan' or 'Winona is a wolf' but not both.
It is impossible that either 'Brian is a swan' or 'Winona is a wolf' 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
  0.05::factA.
  1.0::factB.
  0.7::factC.
  %hop1
  0.9::factX:-or(factC,factB).
  0.75::factY:-xor(factB,factA).
  0.7::factZ:-xor(factA,factB).

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

  query(conclusion).
  
Either 'Brian is a swan' or 'Winona is a wolf' but not both.