Re: some ideas about db rheory

From: rpost <rpost_at_pcwin518.campus.tue.nl>
Date: Mon, 10 Aug 2009 17:09:21 +0000 (UTC)
Message-ID: <h5pk81$fm9$1_at_mud.stack.nl>



Brian wrote:

>On Jul 27, 7:46 pm, rp_at_raampje.(none) (Reinier Post) wrote:
>> 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.
>
>Either there can be change, which implies that there can be things
>that can change, [...]

Yes, there can be change, and there can be things that can change. I am not Parmenides. (Although Parmenides would doubt that.)

>Your argument neither affirms or denies my statement. What it does is
>illustrate the fact that descriptions, such as "Mary's goldfish," can
>refer to different things at different times in the same way that a
>particular instance of a composite key can refer to different things
>at different times--something I've been arguing for a long time.

I completely agree. But what does it mean to say that they are different things? My claim is that what it means you have a *different* model in your mind in which the same thing is represented only once. In other words, you are essentially comparing two different models of the same reality, rather than comparing a model to 'reality itself', something other than a model. This is the mistake pretty much everybody I've ever been pointed to regarding the issue of identity appears to make: they don't realize it's essentially a language feature, and relative to the conceptual model you're using, even if that model is incomplete or informal.

>Because interpreters are temporal beings, interpretations must occur /
>at a time/, which requires that there must be different
>interpretations at different times. Even under the possible worlds
>paradigm, only one possible world at a time can be the actual world.

Only if you make it so by definition of what a possible world is.

[...]

>[...] If there can be things that
>can change, but the system has no way to track identity across
>changes, then the system is broken.

Not if you don't care about that identity. And we need to settle for compromises if we are ever going to settle on a finite conceptual model of anything.

[...]

>Statements are /always/ about things. Each term in a statement is
>assigned something--some...thing--under an interpretation.

Mathematicians traditionally define things that way, but that doesn't make it true. If you stick with it, and fail to recognizing that identity is a feature in a modeling language used to describe the world, rather than the world itself, how are you ever going to get rid of those famous 'logical paradoxes' related to identity?

-- 
Reinier
Received on Mon Aug 10 2009 - 12:09:21 CDT

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