We believe that Emily is a sheep. It is certain that Bernhard is a swan. There is a very good chance that Jeff left the football. It is almost certain that if 'Jeff left the football and Emily is a sheep' then Yann is hungry. It is certain that if either 'Emily is a sheep' or 'Bernhard is a swan' but not both then Julius is yellow. There is almost no chance that if either 'Emily is a sheep' or 'Jeff left the football' but not both then John took the apple.
It is certain that 'Bernhard is a swan' or 'Yann is hungry' or both.
It is certain that 'Bernhard is a swan' or 'Yann is hungry' or both.
It is improbable that 'Bernhard is a swan' or 'Yann is hungry' 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
  0.75::factA.
  1.0::factB.
  0.8::factC.
  %hop1
  0.95::factX:-and(factC,factA).
  1.0::factY:-xor(factA,factB).
  0.02::factZ:-xor(factA,factC).

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

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