It is probably not the case that Fred is in the school. We doubt that Brian is a swan. We believe that Mary left the milk. It is likely that if either 'Mary left the milk' or 'Brian is a swan' but not both then Jason is thirsty. There is a very good chance that if 'Mary left the milk' or 'Brian is a swan' or both then Bernhard is a lion. It is impossible that if 'Fred is in the school' or 'Mary left the milk' or both then Julius is gray.
It is likely that 'Brian is a swan' or 'Bernhard is a lion' or both.
It is likely that 'Brian is a swan' or 'Bernhard is a lion' or both.
Chances are slight that 'Brian is a swan' or 'Bernhard is a lion' 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.
  0.2::factB.
  0.75::factC.
  %hop1
  0.7::factX:-xor(factC,factB).
  0.8::factY:-or(factC,factB).
  0.0::factZ:-or(factA,factC).

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

  query(conclusion).
  
'Brian is a swan' or 'Bernhard is a lion' or both.