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Home -> Community -> Usenet -> comp.databases.theory -> Re: Key attributes with list values was Re: What are the differences ...KEY

Re: Key attributes with list values was Re: What are the differences ...KEY

From: Brian Selzer <brian_at_selzer-software.com>
Date: Mon, 27 Feb 2006 15:56:29 GMT
Message-ID: <NiFMf.37997$F_3.19457@newssvr29.news.prodigy.net>


By revealing an attribute that reflects the identity of a proposition with respect to all other propositions in the database. For lack of a better term, I'll call it an identity attribute. I dislike the term "surrogate" because that implies the existence of an entity, and there is a subtle difference between a surrogate and an identity attribute. A surrogate value indicates that a distinct entity exists; an identity attribute value indicates that a proposition became known by the database. Regardless of the semantics, revealing or adding an additional immutable key is the only mechanism that allows a constraint that involves more than one database state to be enforced by the database.

"Anith Sen" <anith_at_bizdatasolutions.com> wrote in message news:dtv1n8$ie6$1_at_emma.aioe.org...
>>> I really didn't think I needed to state the obvious. The key is the
>>> name of a person. For the purpose of this discussion it doesn't matter
>>> whether it's modeled as a single attribute or two. Only the person's
>>> name and marital status belong to the universe of discourse.
>
> With those propositions, how do you make sure that the DBMS is aware of
> the fact that Jane Harper and Jane Smith are the same entity?
>
> --
> Anith
>
Received on Mon Feb 27 2006 - 09:56:29 CST

Original text of this message

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