Chances are about even that Sandra dropped the milk. It is probable that John went to the kitchen. It is almost certain that Jessica is a mouse. It is probably not the case that if 'John went to the kitchen and Jessica is a mouse' then Mary moved to the garden. There is little chance that if 'Jessica is a mouse' or 'John went to the kitchen' or both then Greg is a rhino. It is probably not the case that if 'Jessica is a mouse and John went to the kitchen' then Julius is a swan.
It is probably the case that either 'John went to the kitchen' or 'Jessica is a mouse' but not both.
It is probably not the case that either 'John went to the kitchen' or 'Jessica is a mouse' but not both.
It is probably the case that either 'John went to the kitchen' 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
  0.5::factA.
  0.7::factB.
  0.95::factC.
  %hop1
  0.25::factX:-and(factB,factC).
  0.1::factY:-or(factC,factB).
  0.25::factZ:-and(factC,factB).

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

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