Chances are slight that Greg is a lion. It is probably the case that John got the apple. We believe that Brian is white. We believe that if 'John got the apple and Brian is white' then Jason is tired. There is a better than even chance that if 'John got the apple' or 'Greg is a lion' or both then Gertrude is a sheep. We believe that if 'John got the apple' or 'Greg is a lion' or both then Julius is white.
There is a very good chance that either 'Jason is tired' or 'Julius is white' but not both.
It is probably not the case that either 'Jason is tired' or 'Julius is white' but not both.
There is a very good chance that either 'Jason is tired' or 'Julius is white' 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
  0.1::factA.
  0.7::factB.
  0.75::factC.
  %hop1
  0.75::factX:-and(factB,factC).
  0.6::factY:-or(factB,factA).
  0.75::factZ:-or(factB,factA).

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

  query(conclusion).
  
Either 'Jason is tired' or 'Julius is white' but not both.