Re: Date's First Great Blunder

"Alfredo Novoa" <alfredo_at_ncs.es> wrote in message news:e4330f45.0404140527.7a608962_at_posting.google.com...
> "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message
news:<c5ia56$t04$1_at_news.netins.net>...
>
> > He suggests that there are two answers given: domain = object class or
> > relvar = object class. He then says that the first equation is
obviously
> > right and the second wrong. Classes are types and domains are types,
but
> > relvars are variables and, therefore, not types, so QED.
>
> It's all very obvious.
>
> > The idea, it seems, is to rid Java programmers of the notion of using
> > classes to define "relations" or records.
>
> The idea is to rid programmers of making great blunders.
>
> > I'm guessing I'm not the only one
> > who doesn't buy Mr. Date's argument.
>
> The vast majority of the OO coders reject the evident when it is
> against the dogma.

OO, like relational database theory, does have religious followers, but I'm guessing that most practitioners of each are more pragmatic than dogmatic, working to develop and maintain information systems. It "works" to specify a "record" by way of an OO class and include persistence methods in the class -- and that is what's "evident" to "the vast majority of the OO coders", I suspect.

> > I'll toss out one of the way-too-many-thoughts buzzing in my head on
this
> > topic. How about this equation:
> >
> > Class = Metadata
> >
> > A class is a spec/template -- not a variable nor an object. There can
be
> > metadata for a type and metadata for a relation/record and classes
> > corresponding to either.
>
> A class is a type and "object" is the mix and confusion of the
> "variable" and "value" concepts.

Is a class a type or a definition of a type? A type, being a domain, is a set. A class is a specification where the set of all objects that can be instantiated using that specification constitute the domain (or the set that actually ARE instantiated, depending on your definition of domain).

> Metadata is data like any other data, and it should be represented in
> the form of relations.

Or in the same for as other data, agreed. Code is metadata..

> > Do many folks agree with Date on this point or is this one of his
> > lone-ranger attempts to push against the OO folks?
>
> This is an attempt to educate the misleaded and misinformed
> practicioners.

Your post is? Date's opinion is? What is? smiles. --dawn Received on Wed Apr 14 2004 - 16:48:06 CEST