It is highly likely that Mary dropped the milk. There is almost no chance that Brian is a frog. It is highly unlikely that Bernhard is a swan. It is unlikely that if 'Bernhard is a swan and Brian is a frog' then Lily is gray. We believe that if 'Mary dropped the milk' or 'Brian is a frog' or both then Jeff went to the bedroom. It is probable that if 'Brian is a frog' or 'Bernhard is a swan' or both then Jason is tired.
It is probable that 'Jason is tired' or 'Brian is a frog' or both.
It is highly unlikely that 'Jason is tired' or 'Brian is a frog' or both.
It is probable that 'Jason is tired' or 'Brian is a frog' 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
  0.9::factA.
  0.02::factB.
  0.05::factC.
  %hop1
  0.2::factX:-and(factC,factB).
  0.75::factY:-or(factA,factB).
  0.7::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Jason is tired' or 'Brian is a frog' or both.