context: It is probable that Bernhard is a swan. There is a very good chance that Brian is green. Chances are about even that John dropped the apple. It is certain that if 'Brian is green and Bernhard is a swan' then Greg is a frog. It is certain that if 'John dropped the apple' or 'Bernhard is a swan' or both then Emily is a mouse. It is impossible that if either 'John dropped the apple' or 'Brian is green' but not both then Jeff went to the bedroom.
hypothesis: Chances are slight that either 'Jeff went to the bedroom' or 'Greg is a frog' but not both.
valid_hypothesis: There is a better than even chance that either 'Jeff went to the bedroom' or 'Greg is a frog' but not both.
invalid_hypothesis: Chances are slight that either 'Jeff went to the bedroom' or 'Greg is a frog' 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
    0.7::factA.
    0.8::factB.
    0.5::factC.
    %hop1
    1.0::factX:-and(factB,factA).
    1.0::factY:-or(factC,factA).
    0.0::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-xor(factZ,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Jeff went to the bedroom' or 'Greg is a frog' but not both.