It is probably not the case that Jason is tired. We believe that Bernhard is a swan. There is a better than even chance that John picked up the apple. There is a very good chance that if either 'Bernhard is a swan' or 'Jason is tired' but not both then Yann is bored. There is little chance that if 'Jason is tired and John picked up the apple' then Mary moved to the garden. It is unlikely that if either 'John picked up the apple' or 'Bernhard is a swan' but not both then Winona is a wolf.
Chances are about even that 'Yann is bored' or 'Mary moved to the garden' or both.
Chances are about even that 'Yann is bored' or 'Mary moved to the garden' or both.
It is highly unlikely that 'Yann is bored' or 'Mary moved to the garden' 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
  0.25::factA.
  0.75::factB.
  0.6::factC.
  %hop1
  0.8::factX:-xor(factB,factA).
  0.1::factY:-and(factA,factC).
  0.2::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'Yann is bored' or 'Mary moved to the garden' or both.