Chances are about even that Brian is yellow. It is unlikely that Bernhard is a frog. It is probable that Greg is white. It is certain that if 'Bernhard is a frog and Brian is yellow' then Yann is thirsty. It is likely that if 'Greg is white and Brian is yellow' then Lily is a swan. There is a better than even chance that if 'Brian is yellow and Bernhard is a frog' then Daniel got the milk.
It is highly unlikely that 'Brian is yellow' or 'Lily is a swan' or both.
Chances are about even that 'Brian is yellow' or 'Lily is a swan' or both.
It is highly unlikely that 'Brian is yellow' or 'Lily is a swan' 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.
  0.2::factB.
  0.7::factC.
  %hop1
  1.0::factX:-and(factB,factA).
  0.7::factY:-and(factC,factA).
  0.6::factZ:-and(factA,factB).

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

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