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Date, Darwen, Pascal and the alternative to Nulls in the RM

From: Paul Mansour <paul_at_carlislegroup.com>
Date: 21 Mar 2006 17:41:29 -0800
Message-ID: <1142991689.461215.270180_at_j33g2000cwa.googlegroups.com> 





Assume one accepts, as I do,  the argument against nulls put forward by
Date et al. Would it be fair to say that at this point in time they
really don't have a solution to missing information?



In the latest edition, just published, of the Third Manifesto (TTM)
Date and Darwen do not include any recommendations on handling missing
information other than pointing to a set of PowerPoint slides by
Darwen, dated 2003.  In fact, as the years go by, each of  Date's
books seem to have stronger and stronger proscriptions against nulls,
and fewer and fewer ideas about how to handle missing information. The
fact that at least 3 years after Darwen's slides on distributed keys
they still did not include the concept in the new TTM book seems a
pretty clear indication that they are really not that confident in the
concept.



Meanwhile, Pascal has 2005 paper "The Final Null in the Coffin",
which seems a bit prematurely named (I haven't read it yet)
considering the fact that it is advertised on his website as only a
starting point or recommendation on how to avoid nulls, and that much
research needs to be done.



So, where does that leave an implementer who does not want to implement
nulls? The leading theorists don't seem to have answers. Their
proposed solutions may well cause more long run damage, just as nulls
did, to the relational model. From nulls to special values, the
proposed cures to missing information may well be worse than the
disease. At this point in time, it seems that the prudent implementer
would prohibit nulls, and essentially leave it up to users to design
well, avoiding inapplicable information, and using application logic
where necessary to handle missing information . Obviously this is not a
good solution, but Date, Darwen and Pascal can't seem to offer
anything better.  Am I wrong here?
Received on Wed Mar 22 2006 - 02:41:29 CET












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