It is likely that Brian is a frog. Chances are slight that Jessica is a cat. It is unlikely that John left the football. We believe that if 'Brian is a frog and John left the football' then Julius is white. Chances are about even that if either 'Jessica is a cat' or 'Brian is a frog' but not both then Greg is a rhino. Chances are about even that if either 'John left the football' or 'Brian is a frog' but not both then Gertrude is a mouse.
It is almost certain that either 'Julius is white' or 'Gertrude is a mouse' but not both.
Chances are about even that either 'Julius is white' or 'Gertrude is a mouse' but not both.
It is almost certain that either 'Julius is white' or 'Gertrude 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.
  0.1::factB.
  0.2::factC.
  %hop1
  0.75::factX:-and(factA,factC).
  0.5::factY:-xor(factB,factA).
  0.5::factZ:-xor(factC,factA).

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

  query(conclusion).
  
Either 'Julius is white' or 'Gertrude is a mouse' but not both.