Re: What does this NULL mean?

"David Cressey" <dcressey_at_verizon.net> wrote in message news:pUdqf.4851$u36.348_at_trndny01...
>
> "mountain man" <hobbit_at_southern_seaweed.com.op> wrote in message
> news:C98qf.72848$V7.1218_at_news-server.bigpond.net.au...
>
>> The only place the RM is evolving is in Date's head, and
>> therefrom in the heads of his party of hangers on. However
>> from an external and independent perspective, the RM has
>> not changed since relational systems started selling oracle.
>
> I disagree. You gave a pointer to an article where Date is compared to
> Codd's paper on adding more meaning to the relational system, leads me to
> believe that Codd has been revising and extending his original vision over
> the years. That pointer was from you, wasn't it?

Possibly, but Codd got most of the substance of the RM in the early days, his later work may have extended it a little, but essentially you could look at his work as refinements of his original vision.

Date was on the spot to document the original vision, but his work appears more akin to pedagogic documentation which is based on Codd's original vision.

It is this pedagogy which has not much altered in 30 years. In that time industry has moved onwards, but the message about the RM and its scope of consideration has changed little.

> However, there is nothing quite so conservative as a successful
> revolution.
> Codd's revisions have been cautious and constructive. I'm not so sure I
> can
> say the same thing about Date&Darwen's revisions.
>
>>
>> > does not address the application software enviroment because it is
>> > completely independent to it.
>>
>> The code and the data are two sides of the one coin.
>> They are like ying and yang. You and Date might like
>> to think they are separate entities with different theoretical
>> basis, but then you and Date have not given the matter
>> enough thought IMO.
>>
>
> Absolutely right.
>
> People whom I regard as smarter than I have attempted to reconcile the
> relational model of data with the object model of process (and
> encapsulated
> data). By their own account, they have not succeeded. Nevertheless, I
> believe that the "data centric" and the "process centric" views will be
> harmonized some time in the future, and I believe the something like the
> object model, but with a firmer theoretical base, will play an important
> role.

I think the writing is on the wall, simply because this is what industry essentially needs in order to be more efficient. In some instances theory leads practice, and in others, practice leads theory.

Up until around 1980, RM theory led practice. But from 1980 practice took on board the principles of the RM and over the following decades refined those principles. Separately Codd refined his vision.

Since the late 1990's IMO practice has lead theory, and has had to contend with many practice components not having any theory available. Process centric models have been helpful, and have been developed outside the RM. The time will eventually arrive when the model of the code and the model of the data will be taken under one theoretical umbrella.

-- 
Pete Brown
Falls Creek
OZ
www.mountainman.com.au