It is probable that Yann is thirsty. It is highly likely that Bernhard is a frog. There is almost no chance that Daniel got the milk. It is highly likely that if 'Daniel got the milk and Bernhard is a frog' then Fred is in the school. It is impossible that if 'Daniel got the milk' or 'Yann is thirsty' or both then Mary left the apple. Chances are about even that if 'Daniel got the milk' or 'Yann is thirsty' or both then Brian is gray.
Chances are slight that 'Yann is thirsty and Bernhard is a frog'.
There is a better than even chance that 'Yann is thirsty and Bernhard is a frog'.
Chances are slight that 'Yann is thirsty and Bernhard is a frog'.

  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.
  0.9::factB.
  0.02::factC.
  %hop1
  0.9::factX:-and(factC,factB).
  0.0::factY:-or(factC,factA).
  0.5::factZ:-or(factC,factA).

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

  query(conclusion).
  
'Yann is thirsty and Bernhard is a frog'.