Re: two nasty schemata, union types and surrogate keys

From: Gene Wirchenko <>
Date: Sat, 26 Sep 2009 14:27:16 -0700
Message-ID: <>

On Fri, 25 Sep 2009 16:33:24 -0700 (PDT), Sampo Syreeni <> wrote:

>Still, to return to my original point, what do y'all think about the
>encoding of facts such as "yes, there are two separate persons called
>John Smith, and no, we don't have any more information about them as
>persons, yet given their sets of cars owned, the one with a Ferrari
>and the one with a Lamborghini are two different persons"?

     If you admit that you can have incomplete data, you would have to admit that the set of cars owned might be incomplete. John Smith 1 and John Smith 2 might be the same person. One of the sets cars owned might be all of the cars that John Smith owned before some date (when his data was collected for entry into the system), and the other set might be his current car. These sets could be disjoint and subsets of all of the cars that John Smith has ever owned.



Gene Wirchenko Received on Sat Sep 26 2009 - 23:27:16 CEST

Original text of this message