context: Chances are about even that Brian is a frog. There is little chance that Greg is green. Chances are about even that Bernhard is yellow. It is highly unlikely that if 'Brian is a frog' or 'Bernhard is yellow' or both then Antoine is thirsty. We believe that if 'Brian is a frog and Greg is green' then Daniel took the apple. Chances are slight that if either 'Bernhard is yellow' or 'Brian is a frog' but not both then John went to the bedroom.
hypothesis: Chances are about even that either 'Brian is a frog' or 'John went to the bedroom' but not both.
valid_hypothesis: Chances are about even that either 'Brian is a frog' or 'John went to the bedroom' but not both.
invalid_hypothesis: It is impossible that either 'Brian is a frog' or 'John went to the bedroom' but not both.
problog: 
    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
    0.5::factA.
    0.1::factB.
    0.5::factC.
    %hop1
    0.05::factX:-or(factA,factC).
    0.75::factY:-and(factA,factB).
    0.1::factZ:-xor(factC,factA).
  
    %hop2
    conclusion:-xor(factA,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is a frog' or 'John went to the bedroom' but not both.