It is probable that Lily is white. There is a very good chance that Brian is a frog. Chances are slight that Julius is gray. There is a very good chance that if 'Brian is a frog and Lily is white' then Mary dropped the milk. There is almost no chance that if 'Brian is a frog and Julius is gray' then John got the apple. It is probably not the case that if 'Brian is a frog and Julius is gray' then Bernhard is green.
It is improbable that 'Brian is a frog and Lily is white'.
There is a better than even chance that 'Brian is a frog and Lily is white'.
It is improbable that 'Brian is a frog and Lily is white'.

  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.
  0.8::factB.
  0.1::factC.
  %hop1
  0.8::factX:-and(factB,factA).
  0.02::factY:-and(factB,factC).
  0.25::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Brian is a frog and Lily is white'.