We believe that Sandra dropped the milk. It is highly likely that Brian is a lion. Chances are about even that Bernhard is yellow. It is certain that if 'Brian is a lion' or 'Bernhard is yellow' or both then Greg is a swan. It is impossible that if 'Bernhard is yellow' or 'Sandra dropped the milk' or both then Winona is a sheep. Chances are slight that if 'Brian is a lion' or 'Sandra dropped the milk' or both then Julius is a frog.
It is certain that 'Bernhard is yellow and Winona is a sheep'.
It is impossible that 'Bernhard is yellow and Winona is a sheep'.
It is certain that 'Bernhard is yellow and Winona is a sheep'.

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

  %hop2
  conclusion:-and(factC,factY).

  query(conclusion).
  
'Bernhard is yellow and Winona is a sheep'.