Re: Proposal: 6NF

Hugo Kornelis <hugo_at_perFact.REMOVETHIS.info.INVALID> wrote:

>On Sat, 14 Oct 2006 18:32:44 GMT, David Cressey wrote:
>
>>"Hugo Kornelis" <hugo_at_perFact.REMOVETHIS.info.INVALID> wrote in message
>>news:0n10j2dk19fibufr8agj3ah5qee6rpm444_at_4ax.com...
>>> On Fri, 13 Oct 2006 04:17:48 GMT, David Cressey wrote:
>(snip)
>>> >Get rid of the Boolean value UNKNOWN.
>>> >Evaluate booleans that can be evaluated to either TRUE or FALSE. If a
>>> >Boolean expression cannot be evaluated, don't return any value at all.
>>> >If there's no trapping mechanism, then return NULL, indicating that the
>>> >expression has no value.
>>>
>>> Hi David,
>>>
>>> Would NULL as a result from a boolean expression differ only in name
>>> from the current UNKNOWN, or would it actually behave differently? For
>>> example, what would the result be of the boolean expression:
>>> (1 > 2) AND (3 = NULL) AND (4 < 5)
>>> or, shorter,
>>> TRUE AND NULL AND FALSE
>>>
>>
>>It's a good question, but I don't have a good answer.
>>My guess is that TRUE AND NULL AND FALSE would have to yield NULL. NULL
>>isn't "TRUE or FALSE but we don't know which". It's the absence of a value.
>
>Hi David,
>
>Okay, that's clear. AFAICT, this is a systematic way to treat missing
>data. Just as SQL's UNKNOWN is a systematic approach of said problem.
>Neither of them is free flom flaws, though - but to be honest, I doubt
>if it's even possible to define a flawless way to handle missing data,
>because the best way to handle missing data varies on a case by case
>basis.
>
>Personally, I prefer UNKNOWN over NULL as third value in 3VL. If only
>because the answers more often match my "common snese" answers. As an
>example, suppose someone would say: "Anyone raise their hand if one of
>the following is true: Seven is less than eight, David Cressey has ever

                        ^^^^^^^^^^^^^^^^^^^^^^^^
     Not false!

>posted to cdt, Mrs Smith from 17th Avenue, NY has had bacon and eggs for
>breakfast today". I would raise my hand because FALSE OR TRUE OR UNKNOWN

                                                 ^^^^^
     Say what?

>evaluates to TRUE. You would keep it down because FALSE OR TRUE OR NULL
>evaluates to NULL.

     Please tell me that you meant "EIGHT is less than SEVEN".

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

     I have preferences.
     You have biases.
     He/She has prejudices.