Re: some ideas about db rheory
Date: Tue, 28 Jul 2009 05:24:21 GMT
"none (Reinier Post)" <rp_at_raampje.> wrote in message
> I wrote:
>>> [...] if you have no way to track identity across changes
>>> in real life, adding it as a modeling feature (either with explicit
>>> identities or by distinguishing between updates and deletes+inserts,
>>> as Brian proposes) isn't going to help a bit.
> Brian replies:
>>[...] Either there can be change, which implies that there can be
>>things that can change, or there cannot be change, which means that
>>there cannot be deletes or inserts, let alone updates.
> No, Brian. These deletes, inserts, and updates are about statements
> of fact about the world, which can change to reflect new or changed
> observations, even when we haven't identified any objects that these
> statements are about to the extent you appear to deem necessary. I can
> observe Mary's goldfish and its medical condition, and truthfully record
> that in my database, two days in a row, *regardless of* whether I can
> tell whether we're dealing with the same goldfish in both cases.
> We may choose not to care and it won't be a problem.
> But for goldfish, at least we know they are identifiable in principle.
> This is not so easy for other types of objects; say, species of fish,
> countries of the world, or clouds.
I've looked at clouds from both sides now, from up and down, and still
It's cloud illusions I recall. I really don't know clouds, at all. Received on Tue Jul 28 2009 - 07:24:21 CEST