It is unlikely that Fred left the football. We believe that Lily is a swan. It is improbable that Bernhard is a rhino. It is unlikely that if 'Fred left the football' or 'Bernhard is a rhino' or both then Mary is in the school. There is a better than even chance that if either 'Bernhard is a rhino' or 'Lily is a swan' but not both then Jessica is a mouse. It is impossible that if 'Lily is a swan' or 'Fred left the football' or both then Julius is gray.
We believe that 'Lily is a swan' or 'Julius is gray' or both.
We believe that 'Lily is a swan' or 'Julius is gray' or both.
Chances are slight that 'Lily is a swan' or 'Julius is gray' 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
  0.2::factA.
  0.75::factB.
  0.1::factC.
  %hop1
  0.2::factX:-or(factA,factC).
  0.6::factY:-xor(factC,factB).
  0.0::factZ:-or(factB,factA).

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

  query(conclusion).
  
'Lily is a swan' or 'Julius is gray' or both.