It is unlikely that Lily is green. It is certain that Greg is a swan. It is probably not the case that Jessica is a sheep. It is almost certain that if 'Lily is green' or 'Greg is a swan' or both then Emily is a cat. There is little chance that if either 'Jessica is a sheep' or 'Greg is a swan' but not both then Mary went to the kitchen. There is a very good chance that if 'Jessica is a sheep and Lily is green' then John moved to the office.
We doubt that either 'John moved to the office' or 'Greg is a swan' but not both.
It is almost certain that either 'John moved to the office' or 'Greg is a swan' but not both.
We doubt that either 'John moved to the office' or 'Greg is a swan' 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.
  1.0::factB.
  0.25::factC.
  %hop1
  0.95::factX:-or(factA,factB).
  0.1::factY:-xor(factC,factB).
  0.8::factZ:-and(factC,factA).

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

  query(conclusion).
  
Either 'John moved to the office' or 'Greg is a swan' but not both.