It is highly likely that Daniel dropped the milk. It is highly likely that Julius is white. Chances are about even that John left the football. It is unlikely that if 'Daniel dropped the milk and John left the football' then Greg is yellow. It is probably not the case that if either 'Daniel dropped the milk' or 'Julius is white' but not both then Brian is a swan. It is probably not the case that if either 'Daniel dropped the milk' or 'Julius is white' but not both then Jeff discarded the milk.
It is almost certain that 'Daniel dropped the milk' or 'John left the football' or both.
It is almost certain that 'Daniel dropped the milk' or 'John left the football' or both.
It is unlikely that 'Daniel dropped the milk' or 'John left the football' 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
  0.9::factA.
  0.9::factB.
  0.5::factC.
  %hop1
  0.2::factX:-and(factA,factC).
  0.25::factY:-xor(factA,factB).
  0.25::factZ:-xor(factA,factB).

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

  query(conclusion).
  
'Daniel dropped the milk' or 'John left the football' or both.