It is probably the case that Julius is green. We believe that Lily is gray. Chances are slight that Jeff discarded the milk. It is probably the case that if 'Jeff discarded the milk' or 'Julius is green' or both then Greg is a swan. Chances are slight that if 'Lily is gray and Julius is green' then John moved to the garden. It is highly unlikely that if either 'Jeff discarded the milk' or 'Julius is green' but not both then Mary left the milk.
It is improbable that 'Mary left the milk' or 'Jeff discarded the milk' or both.
It is improbable that 'Mary left the milk' or 'Jeff discarded the milk' or both.
It is likely that 'Mary left the milk' or 'Jeff discarded the milk' 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.
  0.75::factB.
  0.1::factC.
  %hop1
  0.7::factX:-or(factC,factA).
  0.1::factY:-and(factB,factA).
  0.05::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Mary left the milk' or 'Jeff discarded the milk' or both.