Chances are about even that Julius is yellow. It is impossible that Greg is a swan. It is certain that Jeff went to the bedroom. It is probably not the case that if 'Jeff went to the bedroom' or 'Greg is a swan' or both then John moved to the office. It is probably the case that if 'Greg is a swan' or 'Jeff went to the bedroom' or both then Brian is a frog. It is highly likely that if 'Julius is yellow' or 'Jeff went to the bedroom' or both then Mary got the milk.
It is probably not the case that 'Mary got the milk' or 'Julius is yellow' or both.
It is almost certain that 'Mary got the milk' or 'Julius is yellow' or both.
It is probably not the case that 'Mary got the milk' 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
  0.5::factA.
  0.0::factB.
  1.0::factC.
  %hop1
  0.25::factX:-or(factC,factB).
  0.7::factY:-or(factB,factC).
  0.9::factZ:-or(factA,factC).

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

  query(conclusion).
  
'Mary got the milk' or 'Julius is yellow' or both.