Re: What is analysis?

"TroyK" <cs_troyk_at_juno.com> wrote in message news:093fb5b1-df05-454a-80e5-ae59dd962e9e_at_d27g2000prf.googlegroups.com...
> On Dec 5, 8:25 am, "David Cressey" <cresse..._at_verizon.net> wrote:
> > "Jon Heggland" <jon.heggl..._at_ntnu.no> wrote in message
> >
> > news:fj641f$m36$1_at_orkan.itea.ntnu.no...
> >
> > > Bob Badour answered this; I'll just add a quote from Date's
Introduction
> > > to Database Systems (2004):
> >
> > > In his [1970] paper, Codd uses the term /time-varying relations/ in
> > > place of our preferred /relation variables/ (relvars). But
/time-varying
> > > relations/ is not really a very good term. First, relations as such
are
> > > /values/ and simply do not "vary with time" (there is no notion in
> > > mathematics of a relation having different values at different times).
> > > Second, if we say in some programming language, for example, DECLARE N
> > > INTEGER ; we do not call N a "time-varying integer", we call it an
> > > /integer variable/.
> >
> > > (End quote)
> >
> > Thanks for the above I'm going to try to incorporate "relvar" into my
> > vocabulary, at the expense of misusing it several times in public. Be
> > forgiving, while correcting me.
> >
> > So far, I see at least one way in which the terminology can help my
> > thinking.
> >
> > There is no particular reason why a relvar has to be either persistent
or
> > stored in a database.
> > This allows one to discuss the logical features of data that is shared,
> > whether or not that sharing is mediated by a database and a DBMS. It's
> > always seemed to me that much of "database theory" has really been
about
> > "the theory of data sharing" rather than about storage, retrieval, and
> > persistence as such. Many of the more interesting discussions in this
> > newsgroup would still be interesting even if the data were transferred
from
> > one partner to another over some kind of "message bus" and never stored
in
> > a database at all!
> >
> > So adding "relvars" to my vocabulary will allow me to think, at least
> > primitively, about logical relational models at the application level
and
> > not just at the database level. It seems to me that this is where the
> > battle between relational enthusiasts and object enthusiasts is really
being
> > waged, anyway.

>

>

Thanks.

> I've used a "relations as first class programming citizens"
> programming model to very good effect for iterative application
> development.
>

Did you mean "relvars as first class programming citizens"? Sorry to be so picky, but I really am trying to come up to speed on the term "relvars".

Regardless of the answer, I'm interested in your expriences. Are there any programming languages that support relvars?

> TroyK
Received on Wed Dec 05 2007 - 20:28:17 CET