Re: Codd and many-valued logics

On Friday, June 3, 2016 at 12:51:14 AM UTC-7, Nicola wrote:
> From a theoretical point of view, though, one may legitimately
> wonder about the relationship between SQL with nulls and 3VLs in the
> same way as we know the relationship between SQL without nulls and
> classical logic, at least for a fragment of SQL.

Is there a connection between SQL with nulls and 3VLs? The former is about peculiar values in the domain, and the later is about extra logical value. 3VL has been introduced for propositional logic, and has been extended to predicate calculus. The straightforward interpretation of 3VL in terms of relations and tuples would be tuples equipped with weights which are 3 valued (either tuple is member of a relation, or tuple not belonging to relation, tuple is fuzzy member of the set). This is different from SQL where tuples have some omitted values (nulls) but their membership in the set is sharp (not fuzzy). Received on Fri Jun 03 2016 - 15:56:09 CEST