Re: A pk is *both* a physical and a logical object.

From: paul c <toledobythesea_at_oohay.ac>
Date: Thu, 26 Jul 2007 13:33:16 GMT
Message-ID: <wo1qi.7977$fJ5.772@pd7urf1no>

David Cressey wrote:
> "Brian Selzer" <brian_at_selzer-software.com> wrote in message
> news:DjPpi.24618$Rw1.11254_at_newssvr25.news.prodigy.net...
>
>

>>This illustrates what happens when the only key on a relation schema

>
> permits
>

>>updates.  It can't be determined if a new individual is being selected, or
>>if the state of the current individual is now different.

>
>
> This is the point I have been trying to make for the past week or so. The
> mathematics of the relational data model don't, in this case, disambiguate
> two profoundly different scenarios in the real world the data purports to
> describe.
> ...

David, what does it matter?

The user/audience can agree to disambiguate/interpret however it suits their purpose/application.

What is the possible usefulness of using this term "rigid" to describe a key?

p Received on Thu Jul 26 2007 - 08:33:16 CDT