It is probably not the case that Julius is white. It is certain that Greg is a swan. There is little chance that Mary left the football. It is probable that if either 'Julius is white' or 'Mary left the football' but not both then Winona is a mouse. Chances are about even that if 'Julius is white and Mary left the football' then John took the apple. It is probably not the case that if either 'Julius is white' or 'Greg is a swan' but not both then Lily is green.
It is impossible that 'John took the apple and Winona is a mouse'.
It is impossible that 'John took the apple and Winona is a mouse'.
It is certain that 'John took the apple and Winona is a mouse'.

  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
  0.25::factA.
  1.0::factB.
  0.1::factC.
  %hop1
  0.7::factX:-xor(factA,factC).
  0.5::factY:-and(factA,factC).
  0.25::factZ:-xor(factA,factB).

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

  query(conclusion).
  
'John took the apple and Winona is a mouse'.