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Re: Order & meaning in a proposition

From: Tony <andrewst_at_onetel.net.uk>
Date: 6 Apr 2004 06:07:35 -0700
Message-ID: <c0e3f26e.0404060507.f28c331@posting.google.com>


"Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message news:<c4ss37$lfn$1_at_news.netins.net>...
> I broke down and bought the latest Date "An Introduction to Database
> Systems" text. It looks very comprehensive on the one hand and I look
> forward to reading it cover to cover, even though I have read some of it in
> prior versions.
>
> Without having read the entire book, there still seems to be an aspect
> missing that is integral to understanding data -- language. When taking a
> proposition and normalizing it for the purpose of modeling it, there are
> times when information is inadvertently lost or left behind because it is
> not critical. Sample proposition:
>
> Pat is the host who seated the President and the Secretary of the Interior
>
> If we have a relational model for this proposition, we will end up splitting
> this proposition up and will undoubtedly lose the order of those who were
> seated. If Pat seated others too, we will also lose the fact that these two
> seemed to have been seated together or in close proximity of time or place.
> There is nothing explicit about the ordering, nor is it considered
> important, perhaps, for our software application. However, there is an
> ordering here that is not arbitrary -- the President was listed first as an
> indication of the relative importance of the two who were seated. Even if
> Pat seated the Secretary of State later, it is likely relevant that such
> information is in a separate proposition from the one above.
>
> Once we split apart a proposition in such a way that we cannot get the
> original proposition back, even if we THINK we are getting the important
> aspects of it back, we have lost some of the meaning we intended to capture.
>
> This is an off-the-top-of-my-head example of where one might lose
> information when normalizing data and likely not a very good example
> compared to what might be lost in a typical business application. However,
> the point is that the process of normalizing data makes it sometimes
> impossible to retrieve the original propositions, thereby losing some
> information.
>
> A data modeling process that respects the integrity of the stored
> propositions so that they can be retrieved again has something going for it
> that the relational model lacks, it seems. Any thoughts? Thanks. --dawn

Your example demonstrates exactly why language is a POOR way to express a proposition, and hence should not be the basis of a data model. You state that sentence and then claim that it also denotes that:

a) The President was seated first, then the Secretary
b) The President and the Secretary were seated together (maybe)
c) The President and the Secretary were seated at the same time
(maybe)

Well, if it was meant denote any or all of those things it is not at all clear about it. In fact, these seem to be assumptions rather than true inferences. For all I know it might form part of a longer paragraph:

"Pat is the host who seated the President and the Secretary of the Interior. Pat seated the Secretary when he/she arrived at 8pm, and the President half an hour later. The President sat at the top table and the Secretary sat at the bottom table."

Now if the facts are as you believe, then the propositions should be stated as such, e.g.:

Pat is the host
Pat seated the President at time T1 in location L1 Pat seated the Secretary of the Interior at time T2 in location L2

That no longer reads like everyday language, because it is now being precise about what it means, which everyday language does not as a rule. Received on Tue Apr 06 2004 - 08:07:35 CDT

Original text of this message

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