Re: Separate foreign keys with shared ID space

--CELKO-- wrote:

>
> The main property you want in a key is that it is verifiable in the
> reality of the data model. Invariant is very nice, but not actually
> required. Right now, the United States is facing a massive change in
> retail:
>

I basically concur with your assessment. However, the following scenario may provide additional rationale for invariant PK (as well as supporting your verifiable statement):

In some legal jurisdictions it is necessary to keep data for a minimum amount of time (eg: 7 years) in case that data could be used in a law suit. In such instances, the data may be (preferrably is) archived, possibly to a read-only medium, to permit future investigation by authorities.

If the PK is not invariant, a full trace of the changes to the PK is a necessary submission to support the validity of the PK. Without such a trace, or a confirmation that the PK is invariant, the relevance or even validity of the data can be suspect.

Thus I conclude that a business reason for invariant PK can be established if the data is to be, or potentially could be, used in a legal situation.

I am not sure whether the above is under consideration in the United States, but [in some circles] it is quite an issue in Canada and potentially other jurisdictions.

Hans Received on Tue Aug 03 2004 - 00:38:41 CEST