It is unlikely that Gertrude is a mouse. There is almost no chance that Brian is green. It is highly likely that Sandra left the football. It is unlikely that if 'Sandra left the football and Gertrude is a mouse' then Bernhard is a frog. It is certain that if 'Gertrude is a mouse' or 'Sandra left the football' or both then Lily is white. It is highly likely that if either 'Gertrude is a mouse' or 'Brian is green' but not both then John went to the garden.
It is highly unlikely that either 'John went to the garden' or 'Gertrude is a mouse' but not both.
It is highly unlikely that either 'John went to the garden' or 'Gertrude is a mouse' but not both.
It is likely that either 'John went to the garden' 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
  0.2::factA.
  0.02::factB.
  0.9::factC.
  %hop1
  0.2::factX:-and(factC,factA).
  1.0::factY:-or(factA,factC).
  0.9::factZ:-xor(factA,factB).

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

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