We doubt that Greg is a rhino. It is unlikely that Mary dropped the apple. There is a better than even chance that Brian is a frog. There is a very good chance that if either 'Brian is a frog' or 'Greg is a rhino' but not both then Lily is a swan. Chances are slight that if either 'Mary dropped the apple' or 'Brian is a frog' but not both then Jason is tired. It is impossible that if either 'Brian is a frog' or 'Mary dropped the apple' but not both then John went to the hallway.
There is a better than even chance that 'Jason is tired' or 'Brian is a frog' or both.
There is a better than even chance that 'Jason is tired' or 'Brian is a frog' or both.
It is impossible 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
  0.2::factA.
  0.2::factB.
  0.6::factC.
  %hop1
  0.8::factX:-xor(factC,factA).
  0.1::factY:-xor(factB,factC).
  0.0::factZ:-xor(factC,factB).

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

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