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Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

From: Jan Hidders <jan.hidders_at_REMOVE.THIS.ua.ac.be>
Date: 11 Mar 2003 22:21:28 +0100
Message-ID: <3e6e5358.0@news.ruca.ua.ac.be>


Bob Badour wrote:
>"Jan Hidders" <jan.hidders_at_REMOVE.THIS.ua.ac.be> wrote in message
>news:3e6dba19.0_at_news.ruca.ua.ac.be...
>>
>> But you could argue in much the same way that bags are an abstraction
>> from sets. Just like a while can be simulated with goto's, you can
>> simlulate bags with certain sets, so having explicit bags allows you to
>> ignore certain arbititrary details in the simulation. So would you agree
>> that bags are at a higher level of abstraction then sets?
>
>Actually, you have that backward.
>
>{ 0, 1 } == { 1, 0 } == { 0, 1, 1 } == { 0, 1, 0 } == { 1, 1, 1, 1, 1, 1, 1,
>0, 1, 1 }
>
>All of the above bags are low-level physical representations of the same
>set.

Sure, and a bag can also be represented by different sets. You seem to be assuming that "being at a higher abstraction level" is an asymmetric relation. It isn't.

Received on Tue Mar 11 2003 - 15:21:28 CST

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