It is unlikely that Sandra left the football. It is improbable that Greg is gray. It is probable that Lily is a rhino. It is highly likely that if 'Sandra left the football and Greg is gray' then Winona is a mouse. It is highly likely that if either 'Lily is a rhino' or 'Sandra left the football' but not both then John put down the milk. We doubt that if 'Greg is gray and Lily is a rhino' then Brian is a swan.
It is impossible that 'Winona is a mouse and Brian is a swan'.
It is impossible that 'Winona is a mouse and Brian is a swan'.
Chances are about even that 'Winona is a mouse and Brian 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
  0.2::factA.
  0.1::factB.
  0.7::factC.
  %hop1
  0.9::factX:-and(factA,factB).
  0.9::factY:-xor(factC,factA).
  0.2::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Winona is a mouse and Brian is a swan'.