Re: NULLs

"Brian Selzer" <brian_at_selzer-software.com> wrote in message news:w2Ifj.33526$JD.29797_at_newssvr21.news.prodigy.net...
>
> "Marshall" <marshall.spight_at_gmail.com> wrote in message
> news:c9e87539-ecb1-40f4-b921-fff820d9da08_at_q77g2000hsh.googlegroups.com...

> > The connection between the model and what is being modeled is
> > only in our head. We can consider the model without considering
> > what the state of the real world is. Indeed, we can have a model
> > that doesn't even *have* a corresponding real-world aspect. So
> > when we talk about "missing" information, that's an attribute of
> > the map between the model and reality in our head. It's not
> > an aspect or an attribute of the model. At all.
> >
>
> I disagree. With nulls there is an explicit indication that there is
> information that exists but hasn't been supplied. It is not a matter of
> interpretation. Without nulls, there is no explicit indication so it
> becomes a matter of interpretation.
>

I disagree. A null doesn't indicate that information exists. There is always the "not applicable" case, eg the given name of the spouse of a single person. A null, as such, only indicates that space suitable for occupation by an item of data has no data in it. Whether such data exists in the real world or not is beyond the meaning of a null.

The value of normalizing in this regard is that suitable space only exists when there is data to write in it. At that point the question of whether some data "ought to exist" switches from the interpretation of nulls to the OWA/CWA question. Received on Sat Jan 05 2008 - 13:14:45 CET