Re: theory and practice: ying and yang

Alexandr Savinov wrote:
> Tony Andrews schrieb:
> > Alexandr Savinov wrote:
> >
> >>One major problem of declarative approach is that sets do not exist in
> >>reality.
> >
> >
> > What do you mean by that? Of course they do! It is even an everyday
> > term: chess set, tea set, geometry set. And we think in sets all the
> > time: "my friends", "the population of the UK", "pack of cards", ...
> >
> > How can you possibly say that sets "do not exist in reality"?
>
> I mean that we cannot *represent* sets in such a way that they remain
> sets. We can think of a number of things as a set but we are not able to
> store or pass them. We always need some underlying *representation*
> mechanism like arrays.

So by "in reality" you really mean "in today's programming langauages" do you?

Surely the relational model is all about "representing sets"? I don't need to use mechanisms like arrays to work with a relational database.

> Sets do not exist in reality because elements cannot exist in vacuum
> like in set theory. Elements of a set *must* have some coordinates
> (offsets, positions etc.) in order to be qualified as (separate)
> elements. Thus when we say we have a set we normally mean we have some
> representation of them (but we do not care how concretely it is
> organized, particularly, we do not care its order).

Again, it's not clear to me what you mean by "reality". When, in reality, I say I have a set of something (matching drinking glasses, photographs of Beyonce, boxed set of Andy Williams CDs, whatever), I mean I *really* have such a set, located in time and space. I don't mean that I have a "representation" of them at all! Received on Wed Jun 01 2005 - 11:49:35 CEST