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

From: Bob Badour <bbadour_at_golden.net>
Date: Tue, 11 Mar 2003 10:55:12 -0500
Message-ID: <E6oba.87$_T6.5165106@mantis.golden.net>


"Jan Hidders" <jan.hidders_at_REMOVE.THIS.ua.ac.be> wrote in message news:3e6dba19.0_at_news.ruca.ua.ac.be...
> Bob Badour wrote:
> >"Jan Hidders" <jan.hidders_at_REMOVE.THIS.ua.ac.be> wrote in message
> >news:3e6ccb28.0_at_news.ruca.ua.ac.be...
> >> Bob Badour wrote:
> >> >
> >> >A while loop leaves out of consideration several underlying comparison
> >> >and branching operations as well as branching destinations so as to
> >> >attend to the overall operation of repeating a given sequence of
steps.
> >> >
> >> >A goto statement is a direct encoding of an unconditional branch as
one
> >> >might use in conjunction with comparison operations and conditional
> >> >branches to implement a similar repetition.
> >>
> >> Let's see. With GOTOs:
> >>
> >> 1100 IF NOT(<condition>) THEN GOTO 1210
> >> ...
> >> 1200 GOTO 1100
> >> 1210 ..
> >>
> >> With WHILEs:
> >>
> >> WHILE <condition> DO
> >> ...
> >> END WHILE
> >>
> >> So those "several underlying comparison and branching operations" you
talk
> >> about are exactly *two* operations.
> >
> >I count at least three. Comparison. Conditional branch. Unconditional
> >branch.

>
> Comparison? Where do you see a comparison?

<condition>

> >> not comparable to the kind of abstraction that can be obtained with
> >> functions or classes
> >
> >So? Do you have a point? You asked him what makes him think it is a
higher
> >level of abstraction. It is a higher level of abstraction.
>
> Yes, it is.

So your question was an ultimately pointless challenge of an analogy while ignoring the main point. Good work.

> 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.

> The context in which this question arose was the analogy that Lauri made
> between GOTO vs. WHILE and tuple bags vs. tuple sets and the main issue
was
> whether the analogy is a valid one, esp. w.r.t. query optimization.

It was a valid analogy of increased abstraction. Perhaps Lauri does not know enough about compiler optimization techniques to realize that the specific analogy does not offer any optimization advantages, which means the analogy may have been a poor one. Then again, I seem to recall that Lauri already admitted as much.

An analogy is not an argument, per se. It is a clarification. Since you apparently understood the point, I would say that the analogy worked.

Do you have any other meaningless nits to pick? Received on Tue Mar 11 2003 - 09:55:12 CST

Original text of this message

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