Chances are about even that Mary got the apple. Chances are about even that Greg is a lion. It is improbable that Jessica is a cat. There is little chance that if 'Mary got the apple and Greg is a lion' then Lily is a frog. Chances are slight that if either 'Jessica is a cat' or 'Mary got the apple' but not both then John moved to the garden. It is probable that if 'Greg is a lion' or 'Jessica is a cat' or both then Emily is a mouse.
It is probably not the case that either 'Emily is a mouse' or 'Lily is a frog' but not both.
It is probably not the case that either 'Emily is a mouse' or 'Lily is a frog' but not both.
It is certain that either 'Emily is a mouse' or 'Lily is a frog' 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
  0.5::factA.
  0.5::factB.
  0.1::factC.
  %hop1
  0.1::factX:-and(factA,factB).
  0.1::factY:-xor(factC,factA).
  0.7::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'Emily is a mouse' or 'Lily is a frog' but not both.