It is highly likely that Yann is tired. It is certain that Bernhard is a frog. It is likely that Greg is a rhino. There is almost no chance that if 'Yann is tired and Greg is a rhino' then Bill got the milk there. It is highly likely that if 'Bernhard is a frog' or 'Greg is a rhino' or both then Lily is a swan. There is a very good chance that if 'Bernhard is a frog' or 'Yann is tired' or both then Mary went to the hallway.
It is highly likely that either 'Lily is a swan' or 'Mary went to the hallway' but not both.
It is probably not the case that either 'Lily is a swan' or 'Mary went to the hallway' but not both.
It is highly likely that either 'Lily is a swan' or 'Mary went to the hallway' 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
  0.9::factA.
  1.0::factB.
  0.7::factC.
  %hop1
  0.02::factX:-and(factA,factC).
  0.9::factY:-or(factB,factC).
  0.8::factZ:-or(factB,factA).

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

  query(conclusion).
  
Either 'Lily is a swan' or 'Mary went to the hallway' but not both.