It is certain that Greg is a rhino. It is improbable that Bernhard is a swan. It is probably the case that Julius is yellow. There is almost no chance that if either 'Bernhard is a swan' or 'Greg is a rhino' but not both then John discarded the milk. It is highly unlikely that if 'Julius is yellow' or 'Bernhard is a swan' or both then Mary got the football. We doubt that if either 'Bernhard is a swan' or 'Greg is a rhino' but not both then Winona is a sheep.
It is probable that 'Bernhard is a swan and Julius is yellow'.
It is highly unlikely that 'Bernhard is a swan and Julius is yellow'.
It is probable that 'Bernhard is a swan and Julius is yellow'.

  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
  1.0::factA.
  0.1::factB.
  0.7::factC.
  %hop1
  0.02::factX:-xor(factB,factA).
  0.05::factY:-or(factC,factB).
  0.2::factZ:-xor(factB,factA).

  %hop2
  conclusion:-and(factB,factC).

  query(conclusion).
  
'Bernhard is a swan and Julius is yellow'.