Re: a union is always a join!

On Mar 23, 11:09 am, rp..._at_pcwin518.campus.tue.nl (rpost) wrote:
> >> Yes, but what I meant to say is that in general, the tuples
> >> don't really express facts regarding those domain values,
> >> they just help express information about other domain values.
>
> >Tuples do not express facts about domain values. They contain domain
> >values.
>
> Duh.
>
> True, I didn't express myself clearly enough.
>
> But I don't need your lecturing.

Of course I know you know tuples contain domain values. What you didn't seem to know is that they do not express information about domain values, since you wrote the opposite. I'm only being precise and basic to justify my points clearly. I guess you think I'm too basic. But I think that many things you write contradict basics, and that thus basics are relevant to my reply.

> My point is that in a relational
> the tuples of a relation often correspond not just to the
> propositions of an associated predicate, but to observations; explicitly
> asserted, rather than derived information. To propositional logic,
> it's all the same, of course.

Along the way you have said (along with a lot of other stuff I contradict) that there is a distinction relevant to the user between relations that observe changing things, those that observe unchanging things and those that derive from these; and that it is relevant to the user how any of these are implemented. And I have said that there isn't. Other than what the observing (changing and constant) relations represent, to the *user* it's all the same. And treating them them the same eases programming.

philip Received on Tue Mar 24 2009 - 00:27:08 CET