Re: Dawn doesn't like 1NF

From: Dan <guntermann_at_verizon.net>
Date: 7 Oct 2004 12:11:54 -0700
Message-ID: <3e68f717.0410071111.2124b09d_at_posting.google.com>


"Laconic2" <laconic2_at_comcast.net> wrote in message news:<pI2dncO9sK7WpvjcRVn-uQ_at_comcast.com>... [snip]
>
> But the limitation to simple attributes has no such counterpart in the
> mathematics of relations. In particular, a domain can be a domain of
> relations in math. Not in the relational data model of 1970.

I agree in a sense, but not entirely. Set theory treats sets of sets (or domains of sets/relations if you prefer) as elements. This is an important distinction. As an element, values are treated the same way, no matter what the underlying representation.

As I've stated earlier, I've only seen mathematical relations deal with values as elements, not with total underlying structure or representation (even logically) exposed. I'd be interested in getting a better handle on mathematical relations defined in terms of domains having sets as values, as opposed to elements, if anyone has any pointers to references; then I'd like to see it mapped to a system of logic.

Regards,

Dan

>
> When the commercial "relational DBMS" systems came out in the 1980s, all of
> them required that table columns be "simple". Even a blob is "simple" from
> the point of view of the DBMS. From the DBMS point of view, it's just a
> string bytes with no discernable substructure. Sometime since 1990, both
> the theory and the products have relaxed this rule. But it was definitely
> there when I began to work with relational databases. Dawn can speak for
> Dawn.
Received on Thu Oct 07 2004 - 21:11:54 CEST

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