There is a very good chance that Brian is a swan. It is highly unlikely that Jessica is a cat. Chances are slight that Julius is gray. There is almost no chance that if 'Jessica is a cat and Julius is gray' then Greg is yellow. It is impossible that if 'Julius is gray' or 'Jessica is a cat' or both then Lily is green. It is probably not the case that if either 'Brian is a swan' or 'Julius is gray' but not both then Mary left the football.
It is improbable that 'Jessica is a cat' or 'Brian is a swan' or both.
There is a very good chance that 'Jessica is a cat' or 'Brian is a swan' or both.
It is improbable that 'Jessica is a cat' or 'Brian 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
  0.8::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.02::factX:-and(factB,factC).
  0.0::factY:-or(factC,factB).
  0.25::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Jessica is a cat' or 'Brian is a swan' or both.