We believe that Brian is yellow. It is highly unlikely that Julius is a frog. There is little chance that Daniel took the milk. Chances are slight that if 'Daniel took the milk' or 'Brian is yellow' or both then Bernhard is green. There is little chance that if 'Daniel took the milk' or 'Brian is yellow' or both then Fred is in the school. It is likely that if 'Brian is yellow' or 'Julius is a frog' or both then John went to the kitchen.
It is certain that 'Brian is yellow and Julius is a frog'.
It is highly unlikely that 'Brian is yellow and Julius is a frog'.
It is certain that 'Brian is yellow and Julius 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
  0.75::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.1::factX:-or(factC,factA).
  0.1::factY:-or(factC,factA).
  0.7::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Brian is yellow and Julius is a frog'.