Chances are about even that Lily is a swan. It is probable that Yann is hungry. It is likely that Brian is white. It is probably not the case that if 'Yann is hungry' or 'Brian is white' or both then Winona is a sheep. It is impossible that if 'Yann is hungry and Lily is a swan' then Mary moved to the office. We believe that if 'Lily is a swan' or 'Brian is white' or both then Greg is a frog.
We doubt that 'Yann is hungry' or 'Lily is a swan' or both.
There is a very good chance that 'Yann is hungry' or 'Lily is a swan' or both.
We doubt that 'Yann is hungry' or 'Lily is a swan' or both.

  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.
  0.7::factB.
  0.7::factC.
  %hop1
  0.25::factX:-or(factB,factC).
  0.0::factY:-and(factB,factA).
  0.75::factZ:-or(factA,factC).

  %hop2
  conclusion:-or(factB,factA).

  query(conclusion).
  
'Yann is hungry' or 'Lily is a swan' or both.