Re: Pascal/Date
From: paul c <toledobythesea_at_oohay.ac>
Date: Thu, 04 Jan 2007 03:29:12 GMT
Message-ID: <cw_mh.557861$R63.48416_at_pd7urf1no>
>
>
>
> I read this link and the site is excellent. It is sad that it has no
> more updating. I especially found the article called 'MUCH ADO ABOUT
> NOTHING' between Date and Codd and was interested in this below:
>
> 'Now suppose the system supports two kinds of null, "value unknown" and
> "value does not apply" and four-valued logic (4VL), and suppose
> employee Joe's job is unknown. What do we do about Joe's commission?
> It surely must be null--the information is surely missing--but we don't
> know whether that null should be "value unknown" or "value does not
> apply." Perhaps we need another kind of null, and five-valued logic
> .... This argument clearly goes on for ever, leading to an apparent
> requirement for an infinite number of kinds of null. '
>
> I understand why 4VL causes 5th null, but I do not understand why 'this
> argument clearly goes on forever'. What would 6th null represent? If
> someone can help explain why it is 'leading to an apparent requirement
> for an infinite number of kinds of null.' they have thanks from me.
> Sigmund.
>
Date: Thu, 04 Jan 2007 03:29:12 GMT
Message-ID: <cw_mh.557861$R63.48416_at_pd7urf1no>
s.j.lagoe wrote:
> Bruce C. Baker wrote:
>
>>In re Fabian Pascal: Does anyone have any info on the status of >>http://www.dbdebunk.com/index.html ? It hasn't been updated in a /long/ >>time! :-(
>
>
>
> I read this link and the site is excellent. It is sad that it has no
> more updating. I especially found the article called 'MUCH ADO ABOUT
> NOTHING' between Date and Codd and was interested in this below:
>
> 'Now suppose the system supports two kinds of null, "value unknown" and
> "value does not apply" and four-valued logic (4VL), and suppose
> employee Joe's job is unknown. What do we do about Joe's commission?
> It surely must be null--the information is surely missing--but we don't
> know whether that null should be "value unknown" or "value does not
> apply." Perhaps we need another kind of null, and five-valued logic
> .... This argument clearly goes on for ever, leading to an apparent
> requirement for an infinite number of kinds of null. '
>
> I understand why 4VL causes 5th null, but I do not understand why 'this
> argument clearly goes on forever'. What would 6th null represent? If
> someone can help explain why it is 'leading to an apparent requirement
> for an infinite number of kinds of null.' they have thanks from me.
> Sigmund.
>
Induction? Received on Thu Jan 04 2007 - 04:29:12 CET