Two-valued logic

In an attempt to throw the authorities off his trail, joe.celko.RemoveThis@northface.edu (--CELKO--) transmitted:
 > You ought to be able to do something for missing data; it is a fact
 > of life. Date's tricks for avoiding it just don't work. He had a
 > soluton to an old SQL puzzle of mine on <a rel="nofollow" style='text-decoration: none;' href="http://www.dbdebunk.com" target="_blank">www.dbdebunk.com</a> where we
 > wanted the current salary date and the previous salary, but a
 > new-hire (i.e. no previous data) ws to show up as a NULL. He used
 > an actual date for a missing date (1900-01-01 or something); this
 > implied that there was a loooooong time between raises for some
 > personnel.

Darwen has a paper that presents how you can "totally evade" having
any NULLs.
<http://www.hughdarwen.freeola.com/TheThirdManifesto.web/Missing-info-without-nulls.pdf>

But while it "solves," with reasonable elegance, the problem that he
considers a problem, I think it introduces as big as a problem as the
one that went away, namely that it decomposes the data into a whole
set of views that require that applications be cognizant of not one,
not two, but FOUR quite distinct sorts of "emptiness indicators."

That sure looks to me like a 6-Valued-Logic, as opposed to the mere 3
that pop up with NULL. If 3 was a whole lot worse than 2, once you
take it to the power of 4 or 5, 6^5 has got to be a whopping lot
worse...
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