It is highly likely that Jason is tired. There is a very good chance that Mary dropped the apple. There is little chance that John went to the kitchen. It is unlikely that if 'Mary dropped the apple' or 'John went to the kitchen' or both then Lily is green. It is unlikely that if either 'Jason is tired' or 'John went to the kitchen' but not both then Jeff moved to the garden. It is highly likely that if either 'Jason is tired' or 'Mary dropped the apple' but not both then Bernhard is a frog.
We doubt that either 'John went to the kitchen' or 'Jason is tired' but not both.
There is a very good chance that either 'John went to the kitchen' or 'Jason is tired' but not both.
We doubt that either 'John went to the kitchen' or 'Jason is tired' 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.
  0.8::factB.
  0.1::factC.
  %hop1
  0.2::factX:-or(factB,factC).
  0.2::factY:-xor(factA,factC).
  0.9::factZ:-xor(factA,factB).

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

  query(conclusion).
  
Either 'John went to the kitchen' or 'Jason is tired' but not both.