context: There is a better than even chance that Daniel dropped the apple. Chances are about even that Brian is a frog. We believe that Julius is a swan. We believe that if 'Daniel dropped the apple' or 'Brian is a frog' or both then John went to the office. It is improbable that if 'Julius is a swan and Brian is a frog' then Bernhard is yellow. We doubt that if 'Daniel dropped the apple' or 'Julius is a swan' or both then Mary left the football.
hypothesis: It is certain that 'Mary left the football and Julius is a swan'.
valid_hypothesis: Chances are slight that 'Mary left the football and Julius is a swan'.
invalid_hypothesis: It is certain that 'Mary left the football and Julius is a swan'.
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
    0.6::factA.
    0.5::factB.
    0.75::factC.
    %hop1
    0.75::factX:-or(factA,factB).
    0.1::factY:-and(factC,factB).
    0.2::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-and(factZ,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary left the football and Julius is a swan'.