Re: Natural keys vs Aritficial Keys

"David BL" <davidbl_at_iinet.net.au> wrote in message news:f20bd044-adea-41d5-b301-9dd0f57ed736_at_z16g2000prd.googlegroups.com...

> The ORM idea makes the blunder because it assumes incorrectly that the
> values within a set can be identified independently of their value.
> ORM wants to make this assumption so that a variable that records a
> set of values can instead be interpreted as a set of variables.
>

The last several exchanges in this thread have gone over my head. Oddly enough, this last paragraph brings the discussion full circle, back to where I started.

Consider a set of tuples. Or maybe a set of current states of tuple-variables. (That's the part that's over my head.) Now consider a set of simple identifiers, called ID. ID could have values like 1,2,3,... or any other sequence that can be auto generated and guarantees identity. (The word "sequence" rather than the word "set" is intentional here.) Now merge ID with the original set of tuples, by arranging the set in an some arbitrary sequence. now associate the first tuple with the first ID, the second tuple with the second ID, etc. etc. until every tuple in the set has been identified with an ID. Call this the tagged set of tuples.

Now what you have is a set of tuples where the ORM assumption makes sense, after a fashion. The values in the original set can now be identified independently of their value, because each of them has been tagged with this artificial key called ID, one that can be used for identification purposes.

So maybe the practice of starting every table with a field called ID, and one that's autogenerated, obeys some sort of instinct. Maybe ORM obeys the same instinct. And maybe the tendency to make tools that require simple keys obeys the same instinct. If that turns out to be true, the next two questions for me are obvious: do I want to obey this instinct myself? And, if I don't, how to I want to dialogue with somebeody who does?

Incidentally, I think I understand just a little bit about the difference between a variable that records a set of values and a set of variables. In the second case, if I read it right, the cardinality is immutable. In the first case, the cardinality is variable. If I reread what I just wrote in the light of this, some of it needs rewording. Received on Thu May 28 2009 - 13:56:46 CEST