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Re: Conceptual, Logical, and Physical views of data

From: dawn <>
Date: 11 Sep 2005 21:29:25 -0700
Message-ID: <>

David Cressey wrote:
> "dawn" <> wrote in message
> > I know and I apologize for not yet understanding. This pointer issue
> > seems one of the big motivators for relational theory, so I want to
> > "get it". I understand why this was problematic when related to memory
> > locations, but I don't understand the big downside of using logical
> > pointers, reference values, foreign keys -- what's the difference?
> Dawn,
> I have learned, over time, to be cautious when you say there's something you
> "don't understand."
> When I first "met" you in this news group, you were talking about something
> important that you didn't understand, from reading and rereading Codd's 1970
> paper. I think it was about normalization.


> Somewhat foolishly, I trucked on down to the library and reread the Codd
> paper, which I had not looked at for over a decade. I then proceeded to
> explain to you what I thought I understood it to be saying.

and that was much appreciated

> In the subsequent exchanges between you and me, you gave me to understand
> that you knew everything that I knew about relational theory and practice,
> and then some.

I've learned plenty from you, David. I suspect you might not suggest you have learned anything (positive) from me. When I say that I don't understand something, I really mean that I don't understand it. But that doesn't mean that I don't know some of the same facts that you know, that I haven't read a bit on the topic, or that I have no experience in the field. What I'm not understanding is sometimes how someone moved in their logic from one place to another.

At that time, if I recall correctly, I was trying to understand how Codd moved from modeling data using relations to outlawing "repeating groups". With the help I got, I learned a lot. Instead of ending up agreeing with the "no lists" approach, however, I ended up with a better understanding of my own opinions and rationale to back them up.

>From your statement here, I do sense that you think I say "I don't
understand" when I really do understand, but disagree. But every opinion I express is subject to change if I learn what it was I was not understanding that lead someone else to a contradictory opinion. Sometimes it is a definition of terms and sometimes I'm just not getting what someone else is telling me. When I argue the other side of something here, I am not trying to evangelize or teach -- I am trying to learn. In other forums (e.g. with employees, students, in the blog I'll be starting this month, etc) I take more of a teaching stance. In the past couple of days, it took me several rounds before Marshall got through to me. I was feeling bad about that until he told me two cs ph.d's had the same problem I did. I would like to be quicker, but I can only use the gray matter I have.

I think we have a clash in personalities that causes you to distrust me. When I say that I don't understand something, I really think I am not understanding something that I want to understand. Myers-Briggs of INTP here, although recently I tested as INFP (switching from Marie Currie to Lady Diana say the pop psych web pages).

I find it exceedingly irritating that I don't buy into relational theory the way most professionals do. All external factors point to SQL-DBMS tools as being a good way to do business, including IBM, MS, and Oracle and their db customers all investing heavily in these. So, why don't I "get it"? I wanna know, cause either I have a contribution to make (but would need to know my rationale to defend it) with my contradictory opinion, or I have a gap that I need to bridge in order to be on board with the industry.

> You had simply reached the opposite from mine as to the
> merits of the relational data model.

It isn't that simple. I still think I'm not "getting it" and you are. I would like to wake up at some point and have it all as clear to me why all my standard database application data should be modeled according to relational theory or, if that doesn't happen, have enough understanding of why I disagree that I can give a rationale that is more than just "but my experience has been ..." or "but I think ...".

> I do not feel the need to repeat that exercise.

I understand. I sense your frustration with me, but I don't know what to do about it. If you have taken or could take a Myers-Briggs test, I can try to find out how I should hold a dialog with you that would be mutually satisfying. I don't get frustrated with you, but you do get frustrated with me, and I wish that were not the case.

> In my long career, I have taught relational database programming and design
> to literally hundreds of customers and employees of DEC. I've even taught
> this material in Spanish about three times. In the course of that
> experience, I've had to explain why a foreign key is not the same thing as a
> pointer about a half a dozen times.

And I would be very pleased to hear that explanation (although you might tell me that you have already provided such -- I really am having memory issues).

> But I have little, if anything, to teach to you.

You might feel that way, but I have learned quite a bit from you. If you say something and I disagree, should I pretend to agree? If I don't understand how you arrived at a conclusion and want to, should I refrain from asking? I would think your answers to those questions would be "no", right?

> I need not teach you
> anything that you already know to be true. I cannot teach you anything that
> you already know to be false. What's left?

I'm hoping you are going to be willing to tell me what you have taught others is the difference between a pointer and a foreign key. But then I suspect I will have a follow-up question and you will think something like "You can't teach that girl anything!" and we will do the same dance that you don't enjoy.

By the way, if you go to any db-related conferences, let me know in advance which ones (that goes for others of you too) and maybe an in-person meeting would settle this little glitch. I was going to be in Orlando right now for an IBM DB2 conference, but couldn't swing the logistics. cheers! --dawn Received on Sun Sep 11 2005 - 23:29:25 CDT

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