Re: Proposal: 6NF

From: J M Davitt <jdavitt_at_aeneas.net>
Date: Mon, 09 Oct 2006 12:35:59 GMT
Message-ID: <PmrWg.10293$Cq3.2556@tornado.ohiordc.rr.com>

Jan Hidders wrote:
> J M Davitt schreef:
>
>

>>dawn wrote:
>>
>>>Given the definition of NULL that I typically use (with non-SQL based
>>>solutions), NULL is a value and can be modeled mathematically with the
>>>empty set.  In that case, a relation tuple with a NULL is as valid
>>>mathematically as one without.  Agreed?  --dawn
>>
>>Well, if it's merely a matter of definition, then, "No.  Not agreed."

>
>
> Since Dawn defines NULL as the empty set your answer implies that you
> think the empty set is not a value. Why?
>
> -- Jan Hidders
>

Partly (i) NULL is already overused and (ii) the language used on this thread is imprecise.

For instance, the reference to "relation tuple" in the above paragraph: is she distinguishing between tuples in relations and tuples otherwise? What, exactly, does "valid mathematically" have to do with her point?

[I realize I'm arguing against a point not explicitly made.]

Relations can be empty. zero tuples. Tuples can be empty: zero attributes. Can attributes be empty? No, they require a value. And, without treatment of attribute types, we're going to invent a value, name it NULL, and use it as a placeholder whenever we don't have handy another value to put there?

We have, so far, been able to discuss empty relations and tuples without attributes without having to use the word "NULL." Why must we embrace the noxious term just because someone wants to talk about attributes without values? Received on Mon Oct 09 2006 - 07:35:59 CDT