Re: A real world example

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Thu, 17 Aug 2006 14:48:14 GMT
Message-ID: <Ok%Eg.50136$pu3.587336@ursa-nb00s0.nbnet.nb.ca>

David Cressey wrote:
> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
> news:pXJEg.49046$pu3.575264_at_ursa-nb00s0.nbnet.nb.ca...
>

>>My SSN is not me. It is an arbitrary identifier chosen by the IRS to
>>identify tax filings related to my income. It is familiar because I was
>>given a little blue card with it inscribed, and I was instructed to
>>transcribe it to a variety of documents.

>
> Good point. But the real situation is actually even worse.
>
> First, a side issue. The IRS chooses to use the SSN, but it doesn't assign
> it. A new SSN is assigned by the SSA (Social Security Administration).
> Thus, if the SSA screws up, and assigns the same SSN twice, the IRS is now
> stuck.
>
> The IRS got a key that it is locked into by force of habit, but that is
> beyond its control, except to the extent that there is formal collaboration
> between the IRS and the SSA.
>
> All of this may seem beside the point. I think it's right on topic. In
> essence, a key is natural if "they" assign it, and it's surrogate if "we"
> assign it. Defining "we" and "they" is beyond the scope of this comment.
>
> I'm leaving aside yet another topic, and that is that an SSN doesn't,
> technically identidy a person. It identifies a social security account.
> There is expected to be a one-to-one relationship between (relevant) persons
> and social security accounts, and that is why some people use it to
> identify persons.

Technically, all candidate keys identify sets of related facts and not people or external things. There is expected to be a one-to-one relationship between (relevant) people or external things and whatever commonality relates the facts.

The above is as true for paper records and files as it is for computer records and files or for databases. Received on Thu Aug 17 2006 - 09:48:14 CDT