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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 23:15:12 +0100
Message-ID: <3e6e5ff0.0@news.ruca.ua.ac.be>


Jan Hidders wrote:
>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.

Oops. That should be "antisymmetric relation" of course.

Received on Tue Mar 11 2003 - 16:15:12 CST

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