We doubt that Jeff left the apple. There is a better than even chance that Greg is a frog. It is almost certain that Julius is yellow. There is a better than even chance that if 'Julius is yellow and Greg is a frog' then Jason is tired. It is highly unlikely that if 'Jeff left the apple' or 'Greg is a frog' or both then John moved to the office. It is likely that if 'Julius is yellow' or 'Jeff left the apple' or both then Mary discarded the apple.
It is highly unlikely that either 'Jeff left the apple' or 'Mary discarded the apple' but not both.
There is a better than even chance that either 'Jeff left the apple' or 'Mary discarded the apple' but not both.
It is highly unlikely that either 'Jeff left the apple' or 'Mary discarded the apple' 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.
  0.6::factB.
  0.95::factC.
  %hop1
  0.6::factX:-and(factC,factB).
  0.05::factY:-or(factA,factB).
  0.7::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'Jeff left the apple' or 'Mary discarded the apple' but not both.