Re: Two-valued logic

"--CELKO--" <joe.celko_at_northface.edu> wrote in message <news:a264e7ea.0401030843.6b17ecd2_at_posting.google.com>...

> >> However, I don't know if that is really the case or if I just
> happen to be reading the pro-two-valued logic folks. <<
>
> Yep, you are. The entire SQL world is on 3VL and if Cood had his way,
> it would be a 4VL (TRUE, FALSE, "attribute exists for the entity, but
> value not known" and "attribute does not exists for the entity, so
> value cannot exist")

And there are claims that even 4VL will be insufficient:

 URL:http://home.btconnect.com/SiliconDale/silicon10.htm

(The proposed "mark concept" is reminiscent of IEEE floating-point Martians, such as +/-INF, NAN, etc.)

> In fact, there is a whole area of "missing data" theory in the
> literature. Statistics have all kinds of "missing data" values, for
> example.

And all kinds of ways of dealing with "missing data". Should the relational model bake in support for all of them, or if not, then which ones, exactly?

 URL:http://pfc.forestry.ca/profiles/wulder/mvstats/missdata_e.html

--
Joe Foster <mailto:jlfoster%40znet.com>  Wanna buy a Bridge? <http://xenu.net/>
WARNING: I cannot be held responsible for the above        They're   coming  to
because  my cats have  apparently  learned to type.        take me away, ha ha!