context: There is little chance that Julius is gray. There is a very good chance that John put down the milk. There is a better than even chance that Lily is a swan. There is little chance that if 'Lily is a swan' or 'John put down the milk' or both then Greg is a frog. There is little chance that if either 'Julius is gray' or 'John put down the milk' but not both then Gertrude is a mouse. It is likely that if 'Julius is gray and Lily is a swan' then Sandra left the football.
hypothesis: We doubt that 'Greg is a frog' or 'Gertrude is a mouse' or both.
valid_hypothesis: We doubt that 'Greg is a frog' or 'Gertrude is a mouse' or both.
invalid_hypothesis: We believe that 'Greg is a frog' or 'Gertrude is a mouse' 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
    0.1::factA.
    0.8::factB.
    0.6::factC.
    %hop1
    0.1::factX:-or(factC,factB).
    0.1::factY:-xor(factA,factB).
    0.7::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-or(factX,factY).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a frog' or 'Gertrude is a mouse' or both.