It is certain that Sandra dropped the milk. It is certain that Winona is a sheep. We doubt that Julius is green. It is impossible that if either 'Winona is a sheep' or 'Julius is green' but not both then Bernhard is a rhino. It is probable that if 'Winona is a sheep and Sandra dropped the milk' then Mary went to the office. It is highly unlikely that if 'Julius is green and Winona is a sheep' then Greg is a swan.
It is certain that 'Julius is green and Greg is a swan'.
There is almost no chance that 'Julius is green and Greg is a swan'.
It is certain that 'Julius is green and Greg is a swan'.

  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
  1.0::factA.
  1.0::factB.
  0.2::factC.
  %hop1
  0.0::factX:-xor(factB,factC).
  0.7::factY:-and(factB,factA).
  0.05::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Julius is green and Greg is a swan'.