context: It is probable that Bernhard is a frog. We believe that Greg is a rhino. It is highly likely that John left the football. We believe that if 'John left the football and Bernhard is a frog' then Julius is white. Chances are about even that if 'Greg is a rhino and Bernhard is a frog' then Brian is white. It is impossible that if 'Greg is a rhino and John left the football' then Mary went to the office.
hypothesis: It is impossible that 'John left the football' or 'Greg is a rhino' or both.
valid_hypothesis: It is certain that 'John left the football' or 'Greg is a rhino' or both.
invalid_hypothesis: It is impossible that 'John left the football' or 'Greg is a rhino' or 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.
    0.75::factB.
    0.9::factC.
    %hop1
    0.75::factX:-and(factC,factA).
    0.5::factY:-and(factB,factA).
    0.0::factZ:-and(factB,factC).
  
    %hop2
    conclusion:-or(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'John left the football' or 'Greg is a rhino' or both.