context: It is improbable that Gertrude is a cat. It is highly unlikely that Greg is a frog. It is probably the case that Sandra left the apple. Chances are about even that if 'Gertrude is a cat' or 'Greg is a frog' or both then Lily is a swan. We believe that if 'Greg is a frog and Sandra left the apple' then Mary moved to the office. It is unlikely that if 'Gertrude is a cat and Sandra left the apple' then Jessica is a mouse.
hypothesis: We believe that 'Greg is a frog' or 'Lily is a swan' or both.
valid_hypothesis: It is improbable that 'Greg is a frog' or 'Lily is a swan' or both.
invalid_hypothesis: We believe that 'Greg is a frog' or 'Lily is a swan' 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.
    0.05::factB.
    0.7::factC.
    %hop1
    0.5::factX:-or(factA,factB).
    0.75::factY:-and(factB,factC).
    0.2::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-or(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a frog' or 'Lily is a swan' or both.