It is impossible that Yann is tired. Chances are slight that Fred is in the office. We believe that John put down the apple. It is highly unlikely that if 'John put down the apple' or 'Fred is in the office' or both then Emily is a mouse. There is almost no chance that if 'John put down the apple' or 'Yann is tired' or both then Mary went to the garden. It is probably not the case that if 'John put down the apple and Fred is in the office' then Julius is a swan.
Chances are about even that 'Julius is a swan and Fred is in the office'.
There is almost no chance that 'Julius is a swan and Fred is in the office'.
Chances are about even that 'Julius is a swan and Fred is in the office'.

  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
  0.0::factA.
  0.1::factB.
  0.75::factC.
  %hop1
  0.05::factX:-or(factC,factB).
  0.02::factY:-or(factC,factA).
  0.25::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Julius is a swan and Fred is in the office'.