Re: x*x-1=0

In article <95bc3t$jd2$1_at_news.tue.nl>,   hidders_at_win.tue.nl (Jan Hidders) wrote:
>
> You are falling in the "is" trap that I already warned
> you about in previous postings. You are reading the "is defined as" as
> "is" but that is wrong, wrong, wrong. The claim is not that a pair
> <a,b> *is* {a,{b}} but that this constitutes a *model*. And it is
> hardly surprising that there are several models to choose from. That
 is
> always the case with models and it is not a bug but a feature.

I disagree for 2 reasons. It is rare case in science when you have competitive models living at the same time period. Usually one is perceived much superior to the others. Wave/Particle theories in physics is the famous counterexample, but, eventually, they merged together. <a,b> = {a, {b}} vs. <a,b> = {{a}, b} is unresolved 100 years already. Second, what properties of pairs (or ordered sets, in general) could i derive from this model? The only one I can think of is assymetry. Maybe, this is why i despise it.

> > > The expressive power becomes greater.
> >
> > For me this sounds pretty much like "If I rename variables in
 Maxwell
> > equations, then they won't describe electromagnetic waves any more".
>
> The column names are *observables*; you can point to them and see
 them.
> If you are going to ignore some observables in Maxwell's theory then
> the theory becomes a different theory, if not simply meaningless.

IMHO, domains are observable, not column names. Again, the naming of a column (and relations, either;-) is so arbitrary! How could we eliminate this human factor (they always do that in science:-)?

Besides, my relational algebra equations (not those abstract examples that were mentioned in the thread earler, but the ones I derived from realistic SQL) look messy with explicit rename operations in them.

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http://www.deja.com/ Received on Thu Feb 01 2001 - 19:22:08 CET