context: Chances are about even that Bill went to the office. We doubt that Gertrude is a mouse. There is almost no chance that Greg is a swan. Chances are about even that if 'Greg is a swan and Gertrude is a mouse' then Brian is a frog. It is almost certain that if 'Bill went to the office' or 'Gertrude is a mouse' or both then Jeff left the apple. It is probable that if 'Gertrude is a mouse and Bill went to the office' then Lily is yellow.
hypothesis: Chances are about even that either 'Lily is yellow' or 'Brian is a frog' but not both.
valid_hypothesis: It is highly unlikely that either 'Lily is yellow' or 'Brian is a frog' but not both.
invalid_hypothesis: Chances are about even that either 'Lily is yellow' or 'Brian 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
    0.5::factA.
    0.2::factB.
    0.02::factC.
    %hop1
    0.5::factX:-and(factC,factB).
    0.95::factY:-or(factA,factB).
    0.7::factZ:-and(factB,factA).
  
    %hop2
    conclusion:-xor(factZ,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Lily is yellow' or 'Brian is a frog' but not both.