Re: Objects and Relations

From: Cimode <>
Date: 14 Feb 2007 05:12:54 -0800
Message-ID: <>

[Snipped crap from Keith Duggar]

> Nevertheless, for the benefit of other readers if nothing else, let me
> state that Keith has hit the nail on the head.
No. Keith has just once shown more misunderstanding of RM and arrogance.

> 1) Lego blocks are /not/ the same. They always have a different
> location attribute.
BS. LegoBlock are indeed the same if they are to be a relation.

Stating that location attribute is a primary natural key for a LegoBlock is arbitrary and does not reflect the reality of LegoBlocks. Imagine a M:N cardinality between LegoBlock and Location Entity. In that case LocationEntity has a natural identifier (X, Y, Z). The natural identifier of a lego block could be a combination of its shape, color but certainly not its location.

> 2) Hence their x,y,z position attribute always identifies them.

> 3) However this identifer is very hard to record and keep track of,
> even though it exists.
In the mind of people which pointer's obsessed maybe... There is nothing complex about the identifier of a location is a concatenation of XYZ and a referential.

> 4) So we represent it with a surrogate identifer (which is hence just
> an 'untrackable' attribute or, as others refer to it, an unfamiliar
> attribute).
In other words, Surrogate identifier has only the advantage of being *familiar*.

> 5) OID's are hence not needed, and everything is just a value, as it
> should be.

OID = Implementation of Surrogate Key IF AND ONLY IF --> unicity contraint has been implemented on the implementation of the natural key
--> unicity constraint implemented on the OID --> contraint of cardinality implemented 1:1 between the
implementation of the natural key and the OID....

In other words, almost never happens...

> 6) When I finally understood this (and it was a hard mental slog to
> shake off my OO mindset) I found it quite revelationary to my
> perspective on data management.
Guess we all went through this at some point in time...

[rest snipped] Received on Wed Feb 14 2007 - 14:12:54 CET

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