There is little chance that Julius is a swan. It is likely that John dropped the apple. It is probably not the case that Bernhard is a lion. We believe that if 'Julius is a swan' or 'John dropped the apple' or both then Daniel left the milk. It is probably the case that if 'Julius is a swan' or 'Bernhard is a lion' or both then Sandra took the milk. It is probably not the case that if either 'Bernhard is a lion' or 'Julius is a swan' but not both then Jeff moved to the garden.
It is improbable that 'Bernhard is a lion' or 'John dropped the apple' or both.
There is a very good chance that 'Bernhard is a lion' or 'John dropped the apple' or both.
It is improbable that 'Bernhard is a lion' or 'John dropped the apple' 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.
  0.7::factB.
  0.25::factC.
  %hop1
  0.75::factX:-or(factA,factB).
  0.7::factY:-or(factA,factC).
  0.25::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Bernhard is a lion' or 'John dropped the apple' or both.