Re: database integrity

From: Kenneth Downs <knode.wants.this_at_see.sigblock>
Date: Mon, 23 May 2005 21:26:10 -0400
Message-Id: <8icam2-fuv.ln1@pluto.downsfam.net>

mountain man wrote:

> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message
> news:K%6je.95748$hi2.5651565_at_phobos.telenet-ops.be...

>> Kenneth Downs wrote:
>>>
>>> One question on my mind is the change in rules over time.  Do we say:
>>>
>>> 1.  Data is valid if it adheres to all existing biz rules, OR:
>>> 2.  Data is valid if it adheres to rules that were in force when it was
>>> inserted or updated.
>>
>> Very interesting question. I would say that it is the simplest to let the
>> static database constraints be applicable for all the data, and if you
>> want to restrict what can be added (or deleted or updated) then you use
>> dynamic database constraints (or transition constraints, as they are also
>> called) to specify that.

>
> Additionally, in more complex change, the retrospectively entered
> data may need to be addressed and essentially "converted" to conform
> to the implementation of new rules. This conversion will be a once
> off update of the data, to get it to conform to new rules.
>

Can we tie this to some examples?

Here is my example. The column "VAT" is added to orders. In down-to-earth terms, we are going to add a column to a table. What do you assign as a value for existing orders?

-- 
Kenneth Downs
Secure Data Software, Inc.
(Ken)nneth@(Sec)ure(Dat)a(.com)

Received on Mon May 23 2005 - 20:26:10 CDT