Re: Table Design Question

From: Anith Sen (anith_at_bizdatasolutions.com)
Date: 04/28/04 

Date: Wed, 28 Apr 2004 11:54:04 -0500

>> I say there is and as an example I use a VERY common type of data, a
Person. <<

That is where you faulted. Simply proclaiming an entity name without the
pertinent business model will not gather much meat for you. An entity type
namely "Person" in different business contexts impart different meanings,
associate different rules and have different external predicates. Thus,
declaring the invalidity of specific attribute like email address as a key
without contextual details, as this example, is questionable.

>> I'm asking the question: What is a good, valid, natural key for people?
<<

A better one would be: What is a good key for an entity type? The answer: It
depends on the business model where the entity type exists.

>> I'm claiming that there really isn't a good natural key that you can use
as a primary key when dealing with people and that using a generic key is
not only acceptable, but required. <<

Even with the commonly understood meaning of "natural" keys, none of your
arguments go beyond the key selection criteria in my last post.

The point is, any attribute is "natural" or "artificial" only within the
contexts where it is being discoursed & so, being obsessed about attribute
being "natural" or otherwise is mostly meaningless at the logical level.
Based on the business model & data requireents, a competent designer can
admit another attribute as a primary key or dismiss an existing one based on
the criteria of stability, simplicity, familiarity & minimality. 

-- 
Anith
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