It is probable that Mary moved to the garden. We doubt that Julius is gray. There is a better than even chance that John dropped the milk. It is probably not the case that if 'John dropped the milk' or 'Julius is gray' or both then Bill went to the kitchen. It is certain that if 'Mary moved to the garden and Julius is gray' then Winona is a mouse. There is almost no chance that if 'Mary moved to the garden' or 'Julius is gray' or both then Brian is a lion.
It is impossible that 'Julius is gray and Brian is a lion'.
It is impossible that 'Julius is gray and Brian is a lion'.
We believe that 'Julius is gray and Brian is a lion'.

  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.
  0.2::factB.
  0.6::factC.
  %hop1
  0.25::factX:-or(factC,factB).
  1.0::factY:-and(factA,factB).
  0.02::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Julius is gray and Brian is a lion'.