It is improbable that Jessica is a sheep. There is little chance that Julius is a frog. It is probably not the case that Lily is white. There is a better than even chance that if 'Jessica is a sheep and Julius is a frog' then Yann is tired. We doubt that if 'Julius is a frog' or 'Lily is white' or both then Brian is a swan. It is highly unlikely that if 'Lily is white and Julius is a frog' then John took the apple.
It is certain that 'Brian is a swan' or 'Jessica is a sheep' or both.
It is unlikely that 'Brian is a swan' or 'Jessica is a sheep' or both.
It is certain that 'Brian is a swan' or 'Jessica is a sheep' 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
  0.1::factA.
  0.1::factB.
  0.25::factC.
  %hop1
  0.6::factX:-and(factA,factB).
  0.2::factY:-or(factB,factC).
  0.05::factZ:-and(factC,factB).

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

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