Re: One Ring to Bind Them

"Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message news:voJV3cOtzd6AFwdQ_at_thewolery.demon.co.uk...
> In message <nnIDc.125667$Sw.113988_at_attbi_s51>, Marshall Spight
> <mspight_at_dnai.com> writes
> >For example, in another thread someone said (over and over
> >if I remember correctly :-) that if you delete an invoice, all
> >the line items go with it, automatically. Okay, this is the same
> >thing as ON DELETE CASCADE. But sometimes you want
> >ON DELETE RESTRICT. (In other words, if you want to
> >delete a container but it is still containing something, you
> >have to dispose of the contained things first; you can't just
> >throw them away.) Can you do this declaratively in MV? How
> >is it done?
>
> You mean a bit like you can't delete a company if there are any
> outstanding invoices? No that can't (or rather, shouldn't) be done
> natively and declaratively in MV. But I wouldn't call that a "container
> and contents".

Why do you say "shouldn't?" It seems pretty clear to me that a declarative approach is always better than a procedural one. (Dawn? Care to rebut?)

If not container/contents, what terminology would you use?

> Let's give an example - an owner can have multiple cars, and a car can
> have multiple owners.
>
> What I'd do is have an OWNERS field in the CARS file, and declare it as
> an index. So if I want to know who owns a car, I just list the car and
> pull the owners into the listing. If I want to know what cars someone
> owns, I list all cars owned by that person.

What does "declare it an index" mean? Is it like a pointer or foreign key?

> >> But [MV] provides an interesting confluence of
> >> tools and capabilities that render the model very useful in solving business
> >> problems for many people and businesses.
> >
> >This is not so much what is under discussion in this newsgroup.
> >I will readily acknowledge that many people use MV to do useful
> >work, and that they solve business problems, and that they
> >enjoy themselves doing so. They on-topic question is the theoretical
> >basis for the tools. Are they complete? Are they correct? Are they
> >self-consistent?
>
> Are they even *RELEVANT*? Take any theory in PURE mathematics. It's
> complete, it's correct, it's self-consistent. And if it assumes that
> parallel lines in three dimensions can meet, it doesn't break. It just
> models a completely different world to the one we actually live in ...

I'm sorry, you say this why? Because you have traced some lines from one end of the universe to other and checked that they don't meet? Actually, even the very idea of the "world we live in" having lines in it doesn't work for me. Walking around my house, I never saw an infinite sequence of colinear points.

> Relational fits theory fine. MV fits the real world fine.

That statement just seems totally bogus to me. Does subtraction fit the real world? What happens when I subtract 5 lemons from 3 lemons? Do I get -2 lemons? Can you send me a picture of -2 lemons via email; I want to see what they look like.

Marshall Received on Wed Jul 07 2004 - 03:47:48 CEST