Re: database systems and organizational intelligence

"Alan" <alan_at_erols.com> wrote in message news:2hk09hFdml8oU1_at_uni-berlin.de...
> Your comment below is a joke, I hope.
>
> A functional dependency is a property of the SEMANTICS or MEANING of the
> attributes. It occurs at the "business" level. It is something that
business
> people can tell you. Like (a not perfect example, but easy to understand):
> Each person in our company has a Social Security Number, and each Social
> Security Number (SSN) identifies one and only one person. So, in the
> miniworld of our company, we know that the value of an employee's SSN
> uniquely determines the employee's name. Before any entities or tables
are
> created, before any code is written. A functional dependency is a
constraint
> between two sets of attributes within the miniworld of the database (our
> company).
>
> "Functional" in this context means "unique". It has nothing to do with
> functions as you are thinking of them.

When you write down a functional dependency with the little arrow in it, just what does that arrow mean? I was thinking it was a mapping from one to the other. And what's another word for a mapping? Function, perhaps? I've never known "functional" to mean "unique" -- is that your own personal definition or is there some industry use of the term in this way?

> It has zero, nothing, nada, zip to do with code. Nothing at all. Nothing.

It's all code.
It's all data.

Cheers! --dawn Received on Wed May 26 2004 - 21:29:10 CEST