Re: Weak entity types

From: Bob Badour <>
Date: Fri, 17 Aug 2007 10:17:41 -0300
Message-ID: <46c59fb4$0$4052$>

David Cressey wrote:

> "paul c" <> wrote in message
> news:f9bxi.66051$rX4.40692_at_pd7urf2no...

>>Maybe I'm making the above exchange into more than it is but speaking of
>>word choices and not to question my betters but I wish Codd had never
>>used the term "model".  It has so many connotations that are prey to
>>willful twisting, such as "simulation" or even "emulation" that confuse
>>the literalists, mystics as well as OO fans who dwell among minority
>>rest of us into thinking that they can re-create reality in a machine.

> I disagree completely. Back in 1970, Codd added clarity to a discipline
> that was needing more clarity. The use of the word "model" added clarity.
> The twisting of the word came along later. No matter what term Codd had
> used, people whould have twisted it, IMO.
> The people who believed that some sort of graph based system of data was
> sufficient would have continued to believe that, with or without the word
> "model". See the great debate between Bachman and Codd. BTW, I do not
> include Bachman among the "weak minded" that you reference below.
>>Also encourages the weak-minded to dream that just because there are
>>mechanical ways that relations can be manipulated that there must be
>>equally mechanical ways to define useful relations.  The mathematical
>>parallels that people come up with are useful but they remain
>>abstractions by definition.

> It takes a weak mind to fail to grasp that a model is inherently an
> abstraction.
> If you build a 3 foot model of the Titanic, do the toilets flush?
>>Plus they are extremely partial, for
>>instance there doesn't seem to be an algebra that embodies persistence
>>without resorting to using the word "persistence" and I suspect there
>>couldn't be one.  Sometimes I wish Codd had called his invention the
>>relational abstraction, then it might have been more clear that there
>>remains an irreducible element of Picasso's clever madness in all of
>>this, especially when it comes to cutting out the crap.

> BTW, Codd did not "invent" the relational model of data. He points out
> prior use of the relational model in the 1970 paper, IIRC. What was novel
> with Codd was the application of the relational model to the field of large
> scale data banks.
> Quote from the 1970 paper:
> "This paper is concerned with the application of elementary relation theory
> to systems which provide shared access to large banks of formatted data.
> Except for a paper by Childs [1], the principal application of relations to
> data systems has been to deductive question - answering systems. Levein and
> Maron [2] provide numerous references to work in this area.
> In contrast, the problems treated here are those of data independence - the
> independence of application programs and terminal activities from growth in
> data types and changes in data representation � and certain kinds of data
> inconsistency which are expected to become troublesome even in nondeductive
> systems.
> The relational view (or model) of data described in Section 1 appears to be
> superior in several respects to the graph or network model [3, 4] presently
> in vogue for non-inferential systems. It provides a means of describing data
> with its natural structure only -- that is, without superimposing any
> additional structure for machine representation p[urp]oses. Accordingly, it
> provides a basis for a high level data language which will yield maximal
> independence between programs on the one hand and machine representation and
> organization of data on the other. "
> The term "data independence" is also twisted by some object oriented people
> to mean the same thing as what they mean by "encapsulation". Although the
> two terms address parallel issues, they don't mean the same thing.

Just as separation of concerns as been twisted by the aspect oriented cultists. Received on Fri Aug 17 2007 - 15:17:41 CEST

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