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Re: A Question on Integrety

From: Mike Sherrill <MSherrillnonono_at_compuserve.com>
Date: Fri, 19 Dec 2003 09:36:14 -0500
Message-ID: <t336uv8jpu7cl2oggbqm1j5p8j3a0lovjs@4ax.com>


On Wed, 17 Dec 2003 12:21:45 -0000, "Tobes \(Breath\)" <tobin_dont_spam_me_at_breathemail.net> wrote:

>In my limited experiece this is often true. I've often seen businesses want
>to get at least *some* data, even if it's not entirely useful. The idea is
>then to come back and complete the data later.

IME, the idea never bears fruit. Bad data never becomes good data without a *lot* of effort, and the effort is almost wasted when you put the good data into a database where "anything goes (in)".

>So, you have records that
>don't really conform to the "optimal" business rules, but at this time the
>business rules don't have to apply.

You can reverse-engineer rules from data you can insert. It can be an instructive exercise. IME, it's a good way to present problems to management.

>From my viewpoint, it seems that the RDBMS
>is biased toward enforcing integrety on what goes in, rather than supporting
>rules that change throughout an entities lifecycle.

You might be confusing the relational model with the ways database developers have implemented particular databases in SQL.

Maybe you could post some concrete sample data and some concrete constraints as an example of what you'd like.

>> Staging tables don't make sense for data like this. You have to go
>> with a more complex model that segregates assertions of fact from
>> conclusions.
>
>I don't quite understand this statement! Can you explain a little further
>please!?

Assertions and conclusions are different things. Different things, different constraints. Different constraints, different types, different tables, different attributes.

It's the difference between the statements

  1. Foo Barley lives at 123 Main St., Anytown, NY

which is where Foo Barley really lives (a conclusion), and

 b) On 2003-11-12, Baz Fooley said that Foo Barley lives in New York.
 c) infoUSA.com says "Foo Barly lives at 123 Main Ave., Anytown, NY"
 d) Bar Bazley says that Foo Barley lived in San Francisco, AL.

-- 
Mike Sherrill
Information Management Systems
Received on Fri Dec 19 2003 - 08:36:14 CST

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