It is likely that Lily is white. We believe that Brian is a swan. There is almost no chance that Sandra left the football. Chances are slight that if either 'Sandra left the football' or 'Lily is white' but not both then Gertrude is a mouse. It is probably not the case that if 'Brian is a swan' or 'Sandra left the football' or both then Sumit is thirsty. It is almost certain that if either 'Brian is a swan' or 'Sandra left the football' but not both then John moved to the garden.
It is highly unlikely that 'Gertrude is a mouse and John moved to the garden'.
It is highly unlikely that 'Gertrude is a mouse and John moved to the garden'.
There is a better than even chance that 'Gertrude is a mouse and John moved to the garden'.

  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.
  0.75::factB.
  0.02::factC.
  %hop1
  0.1::factX:-xor(factC,factA).
  0.25::factY:-or(factB,factC).
  0.95::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Gertrude is a mouse and John moved to the garden'.