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Re: Constraints and Functional Dependencies

From: paul c <toledobythesea_at_oohay.ac>
Date: Wed, 28 Feb 2007 22:50:01 GMT
Message-ID: <tGnFh.1181578$R63.797691@pd7urf1no>


Sampo Syreeni wrote:
> On 2007-02-28, paul c wrote:
>

>> What is probalistic about it?  I thought I could convert the same TIFF 
>> to a JPEG twice and get the same JPEG both times.

>
>
> Still, the end user might be having two different days. Unlike the DBMS,
> the end user won't be repeating operations exactly. Hence, what the end
> use wants varies from day to day. The "equivalence" between two images
> that he wants varies all the time, and can only be modelled
> probabilistically.
>
> Secondly, by definition you cannot exactly convert the other way around.
> Once you have a JFIF, at best you have an entire, countably infinite
> class of decompressed TIFF's you can convert it into. (Or was it the
> other way around? Either way, it doesn't affect the argument.) Many of
> those resultant TIFF's will also compress into JFIF's which aren't equal
> to the original one, or necessarily in the equivalence class naturally
> induced by the preimage of the resultant instance of JFIF.
> ...

That's all well and good, but how does the fact that a user may change his mind from day to day bear on this? Why can't a user say an image is one of me one day and one of you the next day? Could I not say "I" is an integer and alternatively a rational instead of a TIFF or JPEG without any basic change to the situation? If the db says THREE is ME one day and THREE is YOU the next day, isn't that up to the user?

(Maybe I'm asking stupid questions because I don't understand possrep's or some technicality or even something more fundamental, so rather than belabour what may have nothing to do with possrep's, I'll shut up about   them for now!)

Thanks,
p Received on Wed Feb 28 2007 - 16:50:01 CST

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