It is highly likely that Brian is a swan. We doubt that Sandra dropped the milk. It is probably not the case that Mary went to the garden. There is little chance that if 'Brian is a swan and Mary went to the garden' then Julius is white. It is probable that if 'Mary went to the garden and Sandra dropped the milk' then Lily is green. We believe that if 'Brian is a swan and Mary went to the garden' then John got the football.
It is certain that 'Mary went to the garden' or 'Julius is white' or both.
It is probably not the case that 'Mary went to the garden' or 'Julius is white' or both.
It is certain that 'Mary went to the garden' or 'Julius is white' 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.
  0.2::factB.
  0.25::factC.
  %hop1
  0.1::factX:-and(factA,factC).
  0.7::factY:-and(factC,factB).
  0.75::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Mary went to the garden' or 'Julius is white' or both.