Re: 3vl 2vl and NULL

On Mon, 12 Dec 2005 12:34:34 -0800, Gene Wirchenko wrote:

>On Sat, 10 Dec 2005 00:05:31 +0100, Hugo Kornelis
><hugo_at_pe_NO_rFact.in_SPAM_fo> wrote:
(snip)
>>In all these cases, you run into the problem that Uncle Vernon's age is
>>not in the database. With or without databases, fact remains is that you
>>don't know if Aunt Marge is older, younger or the same age as Uncle
>>Vernon. This proves that, as soon as you allow values to be missing in
>>your database, True and False are no longer the only possible results of
>>a predicate. Reality forces 3VL on you.
>
> No, it does not. "There is no answer" is also a possible answer.
>That is at a different level than the 2VL.
>
> What is one divided by zero?
>
> Have you stopped beating your wife?

Hi Gene,

Good point!

Throughout this discussion, I'm more and more getting the feeling that the NAME of the third value in 3VL has room for improvement.

Changing it from UNKNOWN to UNANSWERABLE (or something else along that gist - I've had several ideas while reading the thread, but can't recall them now) might take away some (but not all!) of the problems.

Best, Hugo

-- 

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