context: It is impossible that Gertrude is a sheep. There is a very good chance that Julius is a lion. It is probable that Bernhard is green. It is highly likely that if 'Julius is a lion' or 'Gertrude is a sheep' or both then Lily is a swan. It is highly likely that if 'Bernhard is green and Gertrude is a sheep' then John discarded the apple. There is little chance that if 'Julius is a lion' or 'Bernhard is green' or both then Greg is a frog.
hypothesis: There is almost no chance that 'Greg is a frog' or 'Julius is a lion' or both.
valid_hypothesis: There is a very good chance that 'Greg is a frog' or 'Julius is a lion' or both.
invalid_hypothesis: There is almost no chance that 'Greg is a frog' or 'Julius is a lion' 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
    0.0::factA.
    0.8::factB.
    0.7::factC.
    %hop1
    0.9::factX:-or(factB,factA).
    0.9::factY:-and(factC,factA).
    0.1::factZ:-or(factB,factC).
  
    %hop2
    conclusion:-or(factZ,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a frog' or 'Julius is a lion' or both.