context: It is certain that Brian is a lion. There is a very good chance that Mary got the football. Chances are about even that John discarded the apple.
hypothesis: It is impossible that 'Mary got the football and John discarded the apple'.
valid_hypothesis: Chances are about even that 'Mary got the football and John discarded the apple'.
invalid_hypothesis: It is impossible that 'Mary got the football and John discarded the apple'.
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
    1.0::factA.
    0.8::factB.
    0.5::factC.
    
  
    %hop2
    conclusion:-and(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary got the football and John discarded the apple'.