Re: CJ Date on Missing Information

From: Anne & Lynn Wheeler <>
Date: Sat, 18 Mar 2006 13:41:34 -0700
Message-ID: <>

"Paul Mansour" <> writes:
> I've just read "The Default Values Approach to Missing Information" in
> Date's Database Writings 1989-1991. I've also noted that in the 8th
> edition of Date's main textbook, he refers to the "special values
> scheme' for handling missing information, and points to an article in
> Database Writings 1994-1997. I don't have the 94-97 book, though I am
> trying to track down a copy, and I'm curious to know if Date's view on
> handling missing information has changed since the 89-91 writings, or
> is it more or less the same. Any comments on this would be appreciated.

old posting that references a dec92 article in database programming and design by date on dealing with unknown values titled "An Explanation of why three-valued logic is a mistake (Why Accept Wrong Answers?)" How to cope with missing values - NULLS? How to cope with missing values - NULLS?

... aka it isn't so much that 3-valued logic is wrong or incorrect ... it might be considered more of a human factors issue where people are much more prone to making mistakes (and therefor getting unexpected or wrong results) in 3-valued logic.

boolean searches of large databases have seen something analogous ... when you might have billions of items and there are 5-8 search terms ... people frequently inverted the meaning of boolean ANDs and ORs (I think that NLM started seeing this by the early 80s, but it became more wide-spread with growth of internet search engines).

a similar but different occurance was some number of the firewall rule specification languages from the mid-90s ... where a frequent and common mistake for people writing firewall rules would be specifications that inverted what they had actually intended (denying things that they wanted to permit and permitting things that they wanted to deny).

it might be considered analogous to road design ... you might have a perfectly good road ... but if people are having a lot of accidents ... they will frequently attempt to change the road (after they give up on trying to change human nature), possibly just attempting to mitigate what ever human factors issues that are actually resulting in the accidents.

Anne & Lynn Wheeler |
Received on Sat Mar 18 2006 - 21:41:34 CET

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