Re: A question for Mr. Celko

On Mon, 19 Jul 2004 10:56:19 -0700, John Jacob wrote:

>> Not all interpretations of 1NF say that they are disallowed. The one
>> that makes the most sense to me says that the value should be atomic
>> from the database's perspective. In that case you can have any value in
>> an attrbute but you are not allowed to "break it open" which means you
>> cannot have the nest and unnest operations from the nested relational
>> algebra.

It isn't. Like I said above, you can have any value in an attribute under this interpretation of "atomic".

> Clearly there are operators
> that allow me to access the components of the value in each case, so why
> does it matter whether the value is a relation, list, struct, etc.,.?

It doesn't. But that is *all* there should be: you have the operators from the flat relational algebra and functions over your domains, including *any* accessors you need, but no more, because otherwise you go beyond FOL.

• Jan Hidders