It is certain that Mary went to the bedroom. Chances are about even that Bernhard is a swan. It is probably the case that Julius is yellow. There is almost no chance that if 'Bernhard is a swan and Julius is yellow' then Jeff moved to the office. It is impossible that if 'Julius is yellow' or 'Bernhard is a swan' or both then John left the football. We believe that if 'Mary went to the bedroom' or 'Julius is yellow' or both then Brian is a rhino.
It is highly unlikely that 'John left the football' or 'Julius is yellow' or both.
It is likely that 'John left the football' or 'Julius is yellow' or both.
It is highly unlikely that 'John left the football' or 'Julius is yellow' 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
  1.0::factA.
  0.5::factB.
  0.7::factC.
  %hop1
  0.02::factX:-and(factB,factC).
  0.0::factY:-or(factC,factB).
  0.75::factZ:-or(factA,factC).

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

  query(conclusion).
  
'John left the football' or 'Julius is yellow' or both.