context: We believe that Gertrude is a mouse. It is certain that Brian is a rhino. It is highly likely that Greg is gray. Chances are about even that if 'Gertrude is a mouse' or 'Greg is gray' or both then John left the football. We believe that if either 'Brian is a rhino' or 'Gertrude is a mouse' but not both then Lily is a swan. Chances are about even that if either 'Greg is gray' or 'Gertrude is a mouse' but not both then Fred dropped the apple.
hypothesis: It is probably the case that 'Fred dropped the apple and Gertrude is a mouse'.
valid_hypothesis: It is highly unlikely that 'Fred dropped the apple and Gertrude is a mouse'.
invalid_hypothesis: It is probably the case that 'Fred dropped the apple and Gertrude is a mouse'.
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
    0.75::factA.
    1.0::factB.
    0.9::factC.
    %hop1
    0.5::factX:-or(factA,factC).
    0.75::factY:-xor(factB,factA).
    0.5::factZ:-xor(factC,factA).
  
    %hop2
    conclusion:-and(factZ,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Fred dropped the apple and Gertrude is a mouse'.