Re: 1GB Tables as Classes, or Tables as Types, and all that refuted

"Paul" <paul_at_test.com> skrev i en meddelelse news:4199bcb4$0$3990$ed2619ec_at_ptn-nntp-reader01.plus.net...
> Jan Hidders wrote:
> > You are so right that it's almost boring. :-) If there had been any real
> > logical problems with letting relational variables play the role of
> > types then it would have not been possible or very difficult to come up
> > with a decent formal data model for that. It wasn't. QED
>
> Isn't Date's "first great blunder" to be seen more as a rule of thumb or
> a software engineering principle rather than as a formal mathematical
truth?

Would be a reasonable conclusion. But mr. Gittens points at the fact that TTM in general presents itself not as "rules of thumb", but as "science" (as in dbdebunk).

Citation from mr. Gittens paper:
<citation>
Date and Darwen presented the maxim: All logical difference are big differences and its corollary All logical mistakes are big mistakes as a guiding principle in their work on the Third Manifesto. The Third Manifesto proceeded to identify what it refers to as the Two Great Blunders :

  a.. Equating relvars and classes
  b.. Mixing pointers and relations (or more specifically allowing database relvars to contain object IDs)
However, in my humble opinion, the argumentation used to substantiate the claim that the alleged blunders are truly to be viewed as blunders is somewhat weak. This opinion is based on the following maxim: logical conclusions should only be drawn from premises which are both logically valid and relevant. Put another way, keeping in mind the maxim, All logical differences are big differences, logically valid conclusions are conclusions based on premises free of fallacies, including fallacies of relevance. </citation>

Thus, the main issue is not whether or not eg. "class = relvar" is a bad rule of thumb, but if or not this is concluded on a logical basis. From a practical view, it doesn't matter much... Received on Tue Nov 16 2004 - 10:27:20 CET