Re: Storing derived and derivable data
Date: Thu, 04 May 2006 20:43:53 -0400
Message-ID: <injqi3-q7o.ln1_at_pluto.downsfam.net>
dawn wrote:
> Is there database theory that includes identification of
>
> 1. the fact that values for an attribute either were or could have been
> derived?
> 2. how values for an attribute were derived?
> 3. how values for an attribute could have been derived?
>
Dawn, hello! Long time no see.
I saw your post and decided it was time to end my long exile, you have
asked the questions that are at the heart of my company and project.
In order to even begin to deal with this question, you have to deal with
the 800lb gorilla called "Normalization", which forbids derived data. I
wrote an essay on that some months ago, which is here:
http://docs.secdat.com/index.php?gppn=Normalization+and+Automation
The states basically that derived data is part of life, and since
normalization can't deal with it, normalization is not enough to guide
serious application development. But you also can't throw it away,
because it gives good things.