It is unlikely that Lily is a rhino. Chances are slight that John dropped the milk. It is almost certain that Greg is a frog. It is highly unlikely that if 'Lily is a rhino and Greg is a frog' then Mary went to the hallway. It is probably not the case that if 'John dropped the milk and Lily is a rhino' then Sumit is thirsty. There is little chance that if 'Greg is a frog and John dropped the milk' then Jessica is a sheep.
It is almost certain that either 'Greg is a frog' or 'Jessica is a sheep' but not both.
It is almost certain that either 'Greg is a frog' or 'Jessica is a sheep' but not both.
It is impossible that either 'Greg is a frog' or 'Jessica 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
  0.2::factA.
  0.1::factB.
  0.95::factC.
  %hop1
  0.05::factX:-and(factA,factC).
  0.25::factY:-and(factB,factA).
  0.1::factZ:-and(factC,factB).

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

  query(conclusion).
  
Either 'Greg is a frog' or 'Jessica is a sheep' but not both.