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Re: Extending my question. Was: The relational model and relational

From: Bob Badour <bbadour_at_golden.net>
Date: Mon, 24 Feb 2003 01:53:28 -0500
Message-ID: <xIj6a.268$2Y.41329766@mantis.golden.net>


"Bernard Peek" <bap_at_shrdlu.com> wrote in message news:fvnVP4JF8UW+Ewwl_at_diamond9.demon.co.uk...
> In message <%EX5a.232$hl5.34162743_at_mantis.golden.net>, Bob Badour
> <bbadour_at_golden.net> writes
> >"Bernard Peek" <bap_at_shrdlu.com> wrote in message
> >news:ixbyZQwB3AW+EwXz_at_diamond9.demon.co.uk...
> >> In message <7Ik5a.164$8e.17186852_at_mantis.golden.net>, Bob Badour
> >> <bbadour_at_golden.net> writes
> >>
> >>
> >> >It's interesting how you are trying to mischaracterize Date as using
> >> >primitive technology. Multisets are demonstrably more primitive than
> >> >relations--simply from the fact that they rely on physical location.
You
> >are
> >> >the one promoting the use of "Roman numerals and shells".
> >>
> >> Multisets may rely on physical location, although that's a special
case.
> >
> >That's a very remarkable statement. By what other means may users of a
dbms
> >using a multiset logical data model make use of duplicates?
>
> Whatever works.

In other words, they don't and you lack the intellectual honesty to simply admit it.

> What they need is a way to select one of the duplicates.

Yes, they need some way to logically identify each individual.

> What that is will depend on whatever other attributes the duplicates
> have. There is no inherent requirement for that to be physical location.

Well, if it's not in the logical model (and with a multiset logical model it's not), where is it? Whatever attributes the duplicates have, in the logical model the duplicates have identical values for all of the attributes. That's what makes them duplicates.

You have hypothesized something other than physical location. I challenge you to offer any other alternative to distinguish logically identical items. You cannot do it.

> >> The general case is that they rely on information outside the database
> >> to distinguish different items.
> >
> >Really? That's quite extraordinary. How does the dbms use this external
> >information in its logical data model?

>

> It's not in the logical data model. How can it use it? But if you accept
> multisets that isn't a problem.

The internal physical representation is not in the logical model either, but the dbms has no problem using that.

I don't accept multisets--sets are better. Sets provide logical identity and physical independence. I am asking you to justify multisets because you seem to argue that they are justifiable.

> >> If that happens to be physical location
> >> then you can add the current latitude, longitude and altitude as a key.
> >
> >Are you being facetious?

>

> That depends on whether you consider a reductio ad absurdam argument to
> be facetiousness.

You have made an absurd statement. But an absurd statement does not a reductio ad absurdum argument make.

> >> There are some practical problems but in theory it's possible. In
> >> practise if you need to distinguish two cans of tuna you create an
> >> identity field, call it "Can Number" and print labels to stick on each
> >> can.
> >
> >I've identified plenty of cans on shelves, but I've never seen a "Can
> >Number". Where might I find one of those?
>
> Probably in a relational database.

In case you hadn't noticed, we were talking about counting them on the shelf and not in a database. Received on Mon Feb 24 2003 - 00:53:28 CST

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