It is impossible that Brian is a lion. It is probable that Bill went to the kitchen. It is unlikely that Lily is a swan. It is probably the case that if 'Bill went to the kitchen and Lily is a swan' then Sandra got the milk. Chances are slight that if 'Bill went to the kitchen' or 'Brian is a lion' or both then Daniel took the apple. There is a better than even chance that if either 'Bill went to the kitchen' or 'Lily is a swan' but not both then Greg is a frog.
It is impossible that either 'Greg is a frog' or 'Bill went to the kitchen' but not both.
Chances are about even that either 'Greg is a frog' or 'Bill went to the kitchen' but not both.
It is impossible that either 'Greg is a frog' or 'Bill went to the kitchen' 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
  0.0::factA.
  0.7::factB.
  0.2::factC.
  %hop1
  0.7::factX:-and(factB,factC).
  0.1::factY:-or(factB,factA).
  0.6::factZ:-xor(factB,factC).

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

  query(conclusion).
  
Either 'Greg is a frog' or 'Bill went to the kitchen' but not both.