Re: object algebra

From: Eric Kaun <ekaun_at_yahoo.com>
Date: Thu, 26 Feb 2004 18:37:07 GMT
Message-ID: <n1r%b.50111$_W2.1251_at_newssvr33.news.prodigy.com>

"Neo" <neo55592_at_hotmail.com> wrote in message news:4b45d3ad.0402241325.6eb056d5_at_posting.google.com...
> If the RDM model does not address NULLs, it is incomplete.

Does TDM address nulls? If not, why not?

> Or there
> are de facto rules governing NULL otherwise vendors could implement
> NULL handling differently causing problems.

Here's the rule: NULLs aren't allowed.

> If you were to code a RDM
> database, you would have to address NULLs. Or do you think otherwise?

I think otherwise. Dataphor folks, feel free to pipe in here.

> Codd is correct about the utility of NULLs with respect to RDM because
> it creates them. If you create something, you are responsible for it
> by default.

Where does RDM create them?

> NULLs do violate relational closure and should not be allowed.
> Because RDM is (slightly) flawed, using it to represent some kinds of
> things results in NULLs. But not with TDM.

I give up. I can't repeat myself again, but I'm going to anyway to avoid a Dennis Miller style rant.

1. Yes, NULLs violate relational closure
2. Yes, they should not be allowed
3. Furthermore, according to Date, they're not allowed
4. Furthermore, Date gives ways to avoid them
5. The eye color set examples are perfectly sound set theory, and thus also

help the matter
6. RDM can represent things without nulls 7. Just because you have a database design X, and encounter some data that won't fit into it, doesn't mean the data model (relational) is wrong. It means your design is wrong.

I can't think of any other way to say it, and the above is the same as I've typed before.

Bob warned me... I knew he was right, and I darn well jumped in anyway... Received on Thu Feb 26 2004 - 19:37:07 CET