It is probably not the case that Mary got the milk. There is a very good chance that Brian is yellow. It is probable that John moved to the garden. There is a very good chance that if 'Brian is yellow and John moved to the garden' then Lily is a swan. We doubt that if either 'John moved to the garden' or 'Brian is yellow' but not both then Julius is a lion. It is unlikely that if 'John moved to the garden and Mary got the milk' then Bernhard is green.
It is certain that 'Brian is yellow and Lily is a swan'.
Chances are about even that 'Brian is yellow and Lily is a swan'.
It is certain that 'Brian is yellow and Lily is a swan'.

  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
  0.25::factA.
  0.8::factB.
  0.7::factC.
  %hop1
  0.8::factX:-and(factB,factC).
  0.2::factY:-xor(factC,factB).
  0.2::factZ:-and(factC,factA).

  %hop2
  conclusion:-and(factB,factX).

  query(conclusion).
  
'Brian is yellow and Lily is a swan'.