Chances are about even that Gertrude is a sheep. There is a very good chance that Sandra took the football. It is impossible that Julius is a swan. We believe that if 'Julius is a swan' or 'Sandra took the football' or both then Mary left the football. It is impossible that if either 'Sandra took the football' or 'Gertrude is a sheep' but not both then Greg is gray. It is improbable that if either 'Julius is a swan' or 'Gertrude is a sheep' but not both then Lily is a lion.
Chances are about even that 'Sandra took the football and Lily is a lion'.
It is highly unlikely that 'Sandra took the football and Lily is a lion'.
Chances are about even that 'Sandra took the football and Lily 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
  0.5::factA.
  0.8::factB.
  0.0::factC.
  %hop1
  0.75::factX:-or(factC,factB).
  0.0::factY:-xor(factB,factA).
  0.1::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Sandra took the football and Lily is a lion'.