Re: In an RDBMS, what does "Data" mean?

"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message news:40bb0d26$0$559$e4fe514c_at_news.xs4all.nl...
> Alfredo Novoa wrote:
>
> >>>... It was mathematically proven
> >>>that it is better than the graph
> >>>based approaches.
> >>
> > mAsterdam wrote:
> >>This is a very strange statement...
> >
> > This is a very basic knowledge taught in every
> > serious database introductory course.
>
> The statement is made in just about every database
> course, without demonstrating it - that's exactly
> what I think is strange about it. If it's proven
> why not give or at least reference the proof?
> The way it is put, it is propaganda, not basic
> knowledge.

Exactly. I've read a lot of what people have suggested is a mathematical proof that relational database theory is good for business. While the mathematical theory itself is fine, the application of it to databases can have no mathematical proof of its usefulness (math does not prove its usefulness!) and seems to also have no scientific proof of its usefulness either. There are exceptions to this, such as logically proving/showing that if you handle functional dependencies one way or another, it affects what changes need to be made when requirements change. So, I use those techniques. There are tradeoffs. You design one way with agility in mind and mitigate the risks.

> >> ... - Better at what?
> > Simplicity
>
> This reduces the statement to
> "It was mathematically proven that it is simpler
> than the graph based approaches." and leaves the
> judgement to the reader/student. An improvement,
> but it still leaves the questions unanswered:
> simpler at what? etc.

There is surely some mathematics that is simpler when putting data into what-once-was-the-def-of-1NF (no repeating groups). But it is also simpler for the logic in retrieving data to have no relation-valued-attributes and yet they have now been tossed into the mix. So, what's simpler? The old version of 1NF or the new version? Is simpler always better? Applying the simplest mathematics to complex problems isn't our goal here.

> >> - What exacltly was proven?
> > That the Relational Model is superior.
> >
> >> - Could you please give a reference?
> >
> > Codd, E. F. and C. J. Date. "Interactive Support for Nonprogrammers:
> > The Relational and Network Approaches." ... 1974 ...
>
> Part of it was quoted at your second url, see below.
> I could only find the abstract on-line.
>
> abstract (from
> http://portal.acm.org/citation.cfm?id=811529&dl=ACM&coll=portal):
> <quote>
>
> The objectives and strategies of the relational and network approaches
> are compared. The status of support for non-programming users is
> examined. General purpose support for such users entails provision of
an
> augmented relationally complete retrieval capability without
branching,
> explicit iteration, or cursors. It is clear how this capability can be
> realized with the relational approach—whether with a formal or
informal
> language interface. It is not at all clear how the network approach
can
> reach this goal, so long as the principal schema includes
owner-coupled
> sets “bearing information essentially”. A relational discipline is
> suggested as a way out for DBTG users.
>
> </quote>
>
> Appearantly the information principle is dicussed avant la lettre there.
> For the people who do not know that cornerstone:
>
> Chris Date in "EDGAR F. CODD 08/23/1923 – 04/18/2003 A TRIBUTE" at
> http://www.dbdebunk.com/page/page/621965.htm :
> <quote>
>
> The concept of essentiality, introduced by Ted in this debate, is
> a great aid to clear thinking in discussions regarding the nature
> of data and DBMSs. In particular, The Information Principle (which
> I heard Ted refer to on occasion as the fundamental principle
> underlying the relational model) relies on it, albeit not very
> explicitly:
>
> The entire information content of a relational database
> is represented in one and only one way: namely, as
> attribute values within tuples within relations.
>
> </quote>
>
> >
http://www.intelligententerprise.com/db_area/archives/1999/992206/online1.jhtml
>
> While this does give some insights in the
> history of the use of 'data model' and
> related terms (for the people here who
> showed interest in that topic), it doesn't
> at all claim to mathematically prove anything.
>
> >
http://www.intelligententerprise.com/db_area/archives/1999/991105/online2.jhtml
>
> Here it gets very interesting. From the overview:
> <quote>
> Of course, the battle between relations and networks is
> ancient history now. (The good guys won.) This fact notwithstanding,
> Codd's paper -- even though it was written over 25 years ago -- is
> still worth reading today as a beautiful example of clear thinking.
> Indeed, it's quite remarkable to see how, on a topic where muddled
> thinking was the norm at the time, Codd was able to do such a good
> job of cutting to the chase and focusing on the real underlying
> issues. Let me elaborate:
>
> * First of all, Codd realized that to compare the very concrete
> CODASYL specifications and the much more abstract relational
> model would be an apples-and-oranges comparison and would
> involve numerous distracting irrelevancies.

Let me guess -- so instead of taking the relational model to an implementation and playing on the IDMS playing field (which would only provide data on once instance of each), he brought CODASYL onto his ball field and then beat it, right? Sorry, I'm getting ahead of you, excited to hear the story unfold.

> * Hence, it would be necessary first to define an abstract
> "network model." The comparison could then be done on a
> level playing field, as it were, in a fair and sensible
> manner.

laughing

> * Codd therefore proceeded to define an abstraction of
> the CODASYL specifications that might reasonably be
> regarded as such a model. (And then, of course, he went
> on to compare that abstraction with the relational model.)
>
> </quote>
>
> Relevancy to the 'mathematical proof' statement under discussion:
> a fair comparison (a precondition for the claimed mathematical proof)
> would require specification on the same (or at least similar) levels of
> abstraction.
>
> I don't know if anybody after this has provided another
> formalization of the network model, so AFAIK this comparison
> stands.
>
> But what exactly is compared? Relational model versus network model for
> interactive support(1) for nonprogrammers. To dissmiss all graph based
> approaches for all purposes based on it is overstretching it, IMO,
> jumping to conclusions.

Absolutely!

> >>I happen to like graph based approaches
> >>for the overall picture and to elicit design
> >>ideas from non-IT professionals.
> >
> > We are talking about very different things. I am not talking about
> > drawings, I am talking about the network and hierarchical approaches.

As I understand it, the purpose of the relational model is to have a way to "view" the structure of the data. It isn't intended to be the way that it is implemented. So, if users (e.g. me) want to view the data in a graph, then that's seems like a good model to use, right?

> Equating network approaches to graph based approaches, for all
> purposes? The network approach is Codd's formalization of the CODASYL
> specification for the purpose of interactive support(1) for
> nonprogrammers, in the documents you referenced.
> (Or should I say pointed me to :-)
>
> To determine wether it possible generalise Codd's comparisons
> to relational approach vs. graph based approach, some
> more levelling is needed. Generalising the stated purpose
> is not trivial, either.
>
> >>>I am completely opposed to faith and other forms of irrationalism. The
> >>>Relational Model is maths not irrational faith.
> >>
> >>Rationalism is as irrational(/rational) as any oher faith.
> >
> > What a nonsense!
>
> Very faithful ;-)

more laughter from the heretic in this corner

>
> I suspect we will not be able to agree on this one.
>
> However, maybe we can try to agree on the
> 'mathematical proof' issue, by clearly
> stating what exactly was proven.

Yes, I think you started to get at it. It sounds like it has been proven that a mathematical relational model is simpler than a corresponding network model so it would be good to get this nailed down in precise terms (and I haven't read all suggested readings, but will look at them soon). Although I do believe this has been proven, I would still like a clear, crisp theorm/proof of "the proof" for relational theory.

Has there been any proof, ever, of the use of the relational model providing for a better realized solution for anything than any other model? It is in the application of the model that I think we lack evidence.

> Anyway, thank you for the nice read.

quite entertaining! --dawn Received on Mon May 31 2004 - 16:02:57 CEST