Re: NULLs: theoretical problems?

On 8 aug, 22:20, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> Jan Hidders wrote:
> > On 8 aug, 21:10, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
> >>Jan Hidders wrote:
>
> >>>On 8 aug, 17:09, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
> >>>>Jan Hidders wrote:
>
> >>>>>On 8 aug, 14:26, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>
> >>>>>>sinister wrote:
>
> >>>>>>>Many discussions point out one deficiency of NULLs: that they collapse
> >>>>>>>multiple, distinct concepts into one ("no value possible," "value missing,"
> >>>>>>>"value not available at this time", etc).
>
> >>>>>>>What are the other theoretical problems? My impression from skimming some
> >>>>>>>threads in this ng is that some anomalies might occur, maybe having to do
> >>>>>>>with NULLs and joins, or NULLs and keys composed of more than one field, but
> >>>>>>>I'm not sure.
>
> >>>>>>The ultimate theoretical problem is a complete lack of any theory
> >>>>>>underpinning NULL.
>
> >>>>>Just to avoid any misunderstandings: there has of course been lots of
> >>>>>theory on certain interpretations of null values, such as the work by
> >>>>>Raymond Reiter and by Joachim Biskup, but not on the specific meaning
> >>>>>(if you can call it that) that they were given in SQL. Whether that is
> >>>>>necessarily a big problem is IMO not so easy to say.
>
> >>>>In other words, some folks accept that NULL exists without any
> >>>>theoretical underpinning and then create theories of interpretation.
>
> >>>Indeed. Because, as we all know, proposing and investigating
> >>>alternatives is the same as accepting something's existence.
>
> >>>>How
> >>>>exactly does that differ from scriptural interpretation and theories
> >>>>thereof?
>
> >>>Exactly! Rejecting straight away null values in any form or shape
> >>>without any sort of investigation of their properties would have been
> >>>much more scientific. :-)
>
> >>That doesn't answer the question. How does it differ from scriptural
> >>interpretation and theories thereof?
>
> > What makes you think they have anything in common?
>
> Each relates to interpretation and to an abstract entity taken as a given.

The mentioned research doesn't take anything as given. They supply definitions of their own.

• Jan Hidders