It is probable that John moved to the garden. It is probable that Bernhard is a swan. We doubt that Julius is a frog. Chances are slight that if either 'John moved to the garden' or 'Julius is a frog' but not both then Mary went to the hallway. Chances are about even that if 'Julius is a frog and John moved to the garden' then Gertrude is a mouse. It is likely that if 'Julius is a frog' or 'Bernhard is a swan' or both then Brian is gray.
It is highly unlikely that 'Julius is a frog' or 'John moved to the garden' or both.
We believe that 'Julius is a frog' or 'John moved to the garden' or both.
It is highly unlikely that 'Julius is a frog' or 'John moved to the garden' or 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.
  0.2::factC.
  %hop1
  0.1::factX:-xor(factA,factC).
  0.5::factY:-and(factC,factA).
  0.7::factZ:-or(factC,factB).

  %hop2
  conclusion:-or(factC,factA).

  query(conclusion).
  
'Julius is a frog' or 'John moved to the garden' or both.