novaBBS - comp.databases.theory - Re: "Theoreticians” are Clueless about Relational Data Modelling, Teach Anti-Relational Muddling

Re: "Theoreticians” are Clueless about Relational Data Modelling, Teach Anti-Relational Muddling

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Subject: Re:_"Theoreticians”_are_Clueless_about_Relational_
Data_Modelling,_Teach_Anti-Relational_Muddling
From: derek.as...@gmail.com (Derek Ignatius Asirvadem)
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by: Derek Ignatius Asirv - Wed, 28 Apr 2021 06:28 UTC

> On Thursday, 22 April 2021 at 08:40:00 UTC+10, Derek Ignatius Asirvadem wrote:
> > On Thursday, 22 April 2021 at 06:27:56 UTC+10, LP wrote:
> >
> > Only one minor detail: I have tried to track the origin of the IEEE
> > symbols for subtyping, but I don't seem to be able to find much
> > information. AFAIK, Information Engineering originally used **nested boxes**
> > (derived from Barker's notation?).
>
> [ explanation, skipped ]
>
> The nested boxes was classic Hierarchic Paradigm ...
>
> Nested boxes meant the designer was using a HDBMS ...
>
> An Hierarchic file consisted of one parent type-of-record, and many child types-of-record ... implemented as a continuous series of records, from the parent record through one bunch of child records; then the next bunch; then the next parent; etc ...
>
> Whereas in the NDBMS, each type-of-record was a separate file, and we had two types of file: Master (key access) and Variable (linked-list chain from the Master). Therefore no nested boxes.

__Nested boxes__ in pre-Relational File Definition diagrams, is not to be confused with:
__Nested Sets__

An abortion, straight from hell. A Record Filing System within a Record Filing system. Not only does this generate masses of duplication and break Normalisation rules, this fixes the records in the filing system in concrete.

Moving a single node requires the entire affected part of the tree to be re-written. Beloved of the Date, Darwen and Celko types.

The MS HIERARCHYID Datatype does the same thing. Gives you a mass of concrete that has to be jack-hammered and poured again, every time a node changes. Perfect for beginners who think that Lego is an implementation method in SQL containers.

Cheers
Derek

Subject	Author
Re: "Theoreticians” are Clueless about Relational	Derek Ignatius Asirvadem

Marriage is the only adventure open to the cowardly. -- Voltaire

devel / comp.databases.theory / Re: "Theoreticians” are Clueless about Relational Data Modelling, Teach Anti-Relational Muddling

devel / comp.databases.theory / Re: "Theoreticians” are Clueless about Relational Data Modelling, Teach Anti-Relational Muddling