It is likely that John moved to the garden. It is likely that Jessica is a mouse. We believe that Jeff went to the bedroom. It is probable that if 'Jeff went to the bedroom and Jessica is a mouse' then Gertrude is a cat. We believe that if 'Jessica is a mouse and Jeff went to the bedroom' then Mary dropped the milk. There is a very good chance that if 'Jessica is a mouse and John moved to the garden' then Bernhard is a rhino.
It is impossible that either 'Jeff went to the bedroom' or 'Jessica is a mouse' but not both.
Chances are about even that either 'Jeff went to the bedroom' or 'Jessica is a mouse' but not both.
It is impossible that either 'Jeff went to the bedroom' or 'Jessica is a mouse' 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
  0.7::factA.
  0.7::factB.
  0.75::factC.
  %hop1
  0.7::factX:-and(factC,factB).
  0.75::factY:-and(factB,factC).
  0.8::factZ:-and(factB,factA).

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

  query(conclusion).
  
Either 'Jeff went to the bedroom' or 'Jessica is a mouse' but not both.