Re: Codd and many-valued logics

On Wednesday, June 8, 2016 at 12:20:56 PM UTC-7, Nicola wrote:

> There is inherent complexity in dealing with uncertain, incomplete, information, no matter how many truth values your logic has.

Yes.

> Codd had good reasons to make certain trade-offs, in the seventies.

No, his work on null and higher-valued logic is and has always been known to be trash.

> In fact, it may be argued that SQL deals with the former type of nulls just fine (see Franconi and Tessaris's, On the Logic of SQL Nulls, 2012).

Fragments and idioms of the SQL system of tables with null plus operators on them have some use, but the overall system is not useful for the intended purpose.

> Not Applicable nulls allow you to use much less predicates (P(A,B) vs P1(A,B), P2(A), P3(B), P4()).

Fewer, but much more complex, considering that instead of a nullable column N you could just have P(A) and P(A,N).

> In some sense, that is the best one can hope for without compromising efficiency.

Yes, that is the big problem.

philip Received on Sun Jun 12 2016 - 10:39:36 CEST