Re: Database design, Keys and some other things

On 29 Sep 2005 14:33:40 -0700, "JOG" <jog_at_cs.nott.ac.uk> wrote:

>Okay fair enough. The issue clearly has baggage. But I have used,
>advocated, and taught the RM for over a decade now, and I am not just
>trying to be contrary. But I'm not doing down the RM - the primary
>attraction of RM os that it was not created in an ad-hoc fashion, but
>rather based on fundamental principles. All my posts were intended to
>be, were a discussion of a different possible principle to base a
>mathematical model upon.

     You are going to have to do better than that. We hear noise about inadequacies of the RM quite frequently. Not much ever comes of the noise.

>Proposition:
>I am putting forward for discussion that Codd's Information Principle
>(based on an Liebniz/essentialist viewpoint that an entity is defined
>by its attributes, and is nothing more and nothing less than the
>aggregate of them, [Celko - D&DB]) is not a complete model of the
>nature of information. Rather I am proposing that there is no single
>attribute of an entity that can be gauranteed to act as a permenant
>immutable reference for it (nominalism - there are no universals), and
>so an external one to represent our concept of an entity be provided.
>
>Difficulties arising from the IP:
>Primary Key non-mutability - often necessary to employ internal
>surrogates that require management [Codd - RM/T paper].
>Lack of Internal Referencing checks - often necessary to explicitly use
>cascade mechanisms to prevent dangling references, orphan records.
>
>Possible Solution:
>provide any encoded proposition with an automated reference that
>guarantees primary key mutability, but is externalised from the data,
>which then remains a pure encoding of the representation of real-world
>attributes (essentially the partial map that is the tuple becomes a
>datatype) [W, Kent - D&R]. Joins may be pivoted on this reference, and
>integrity is continually maintained by the DBMS between these
>references to prevent orphan tuples.

     This appears to be simply the idea of a surrogate key. If it is not, you have explaining ahead of you.

>Now I'm afraid, I have no more than that to offer at the moment. And
>obviously its all up for assassination, and thats no problem, shoot.
>That's why i'm posting - to get your educated opinions. Just don't tell
>me this sort of discussion isn't valid here (where else?), that I don't
>roll my sleeves up and do real work or that the questioning the
>philosophy of axioms is for high school.

     Not me. Have at it. Just do not blow smoke or handwave (much).

Sincerely,

Gene Wirchenko Received on Fri Sep 30 2005 - 00:38:49 CEST