Re: Trying to define Surrogates
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Thu, 17 Aug 2006 16:41:15 GMT
Message-ID: <L_0Fg.50712$pu3.588455_at_ursa-nb00s0.nbnet.nb.ca>
>>JOG wrote:
>>
>>>My name is an identifier for me.
>>>My fingerprint is an identifier for me.
>>>
>>>Say we don't have the ability to digitise the photos we have of
>>>fingerprints. Then we produce:
>>>
>>>532673294 is a identifier for my fingerprint, which is a identifier for
>>>me.
>>>
>>>The 2nd level of indirection in the last line indicates use of a
>>>representative for an attribute that existed naturally before the
>>>design of the database. It is not that it is just wasn't 'familiar', it
>>>didn't exist at all - we have made the domain up specifically to
>>>facilitate the information modelling process. We have not just modelled
>>>the propositions we have added to them.
>>>
>>>That for me is the distinction made when I see the word surrogate in
>>>context of databases.
>>
>>I think this is a fairly specific case where the natural key isn't
>>easily manipulated, but it's a bit of a hack, and a fairly specific
>>case. I think the more common use of a surrogate key is where no
>>natural key exists - to separate cans of Campbell's chicken noodle
>>soup, you need to give them an artificial label. This label sometimes
>>makes it into the real world as well.
Date: Thu, 17 Aug 2006 16:41:15 GMT
Message-ID: <L_0Fg.50712$pu3.588455_at_ursa-nb00s0.nbnet.nb.ca>
JOG wrote:
> erk wrote: >
>>JOG wrote:
>>
>>>My name is an identifier for me.
>>>My fingerprint is an identifier for me.
>>>
>>>Say we don't have the ability to digitise the photos we have of
>>>fingerprints. Then we produce:
>>>
>>>532673294 is a identifier for my fingerprint, which is a identifier for
>>>me.
>>>
>>>The 2nd level of indirection in the last line indicates use of a
>>>representative for an attribute that existed naturally before the
>>>design of the database. It is not that it is just wasn't 'familiar', it
>>>didn't exist at all - we have made the domain up specifically to
>>>facilitate the information modelling process. We have not just modelled
>>>the propositions we have added to them.
>>>
>>>That for me is the distinction made when I see the word surrogate in
>>>context of databases.
>>
>>I think this is a fairly specific case where the natural key isn't
>>easily manipulated, but it's a bit of a hack, and a fairly specific
>>case. I think the more common use of a surrogate key is where no
>>natural key exists - to separate cans of Campbell's chicken noodle
>>soup, you need to give them an artificial label. This label sometimes
>>makes it into the real world as well.
> > are you telling me that two Cans of Campbell's have no identity without > an artificial label? If that were true you would not be able to > distinguish them, yet you can. What, then, is that distinguishing > property?
Location. Received on Thu Aug 17 2006 - 18:41:15 CEST