# Re: The wisdom of the object mentors (Was: Searching OO Associations with RDBMS Persistence Models)

Date: 5 Jun 2006 11:41:04 -0700

Message-ID: <1149532864.012890.166700_at_c74g2000cwc.googlegroups.com>

Bob Badour has clarified what I meant. RM defines clearly separation between operators and operation.

erk wrote:

*> Bob Badour wrote:
**> > I believe Cimode misspoke. The definition of 'operator' as a symbol
**> > signifying an operation is a basic definition in computing--all of
**> > computing. You can verify that in the ISO standard definitions if you
*

> > want to.

*>
**> Is there a link for their computing definitions? Or is it available for
**> purchase only? My googling on this isn't turning up what I need.
**>
**> > > So you're talking about the algebraic definition of a type, like
**> > > pop(push(S, x)) = x for a stack?
**> >
**> > No, he is talking about the definition of a type. An algebra simply
**> > restricts the operations to those defined only on the type. Algebras
**> > have the desirable property of closure, which is very handy for nesting.
**>
**> Hmm... I thought algebras were a little more flexible than that. I
**> certainly understand the value of closure, but the push operation above
**> clearly isn't defined only over the stack domain.
**>
**> > Thus, while length and substring are operations on strings--being
**> > defined using strings and integers--they are not part of either string
**> > or integer algebra. Catenation, on the other hand, is part of the string
**> > algebra.
**>
**> OK. So the above isn't truly a stack algebra? And you couldn't write
**> the following as part of the string algebra? Does the relational
**> algebra truly not involve domains other than relations? It makes
**> reference to at least equality in the domains of attributes, doesn't
**> it?
**>
**> - erk
*

Received on Mon Jun 05 2006 - 20:41:04 CEST