Re: Domain

"Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message <news:bsqv24$r4r$1_at_news.netins.net>...

> "Joe "Nuke Me Xemu" Foster" <joe_at_bftsi0.UUCP> wrote in message
> news:1072725369.339410_at_news-1.nethere.net...

> > Oh no, you're a Pure OOPie-head as well?? =^|
>
> Why thank-you -- but I'm only 99.8% "Pure" ;-) As for Java or other OO
> languages, I like them to the extent that they get the job done. I'm
> comfortable with non-OO languages as well and just as with my angle on
> relational databases, I tend to look at various technologies in terms of
> pros and cons. I don't take on a religious zeal for any technology
> abstractly -- I'm inclined to favor what works in practice. Java works even
> though it is not perfect. SQL works and it falls well below perfect to the
> point where I really dislike the language. I'd rather we start with Java
> than SQL for defining types since what we need seems to be pretty much there
> already.

I don't know about you, but I'd prefer to keep noncircular circles and other inheritance squirrelyness from infecting the database. Some things that might be (barely) acceptable in a general-purpose programming language would be deadly in an RDBMS. Once you allow an inconsistency to creep into a predicate logic system, you can end up "proving" just about *anything*, up to and including 1 = 0.

> > > To answer the original question, without looking up anyone else's
> > > definition, I'd say that a domain is a named set of possible attribute
> > > values for a specified attribute.
> >
> > That sounds more like a "field" with a "validation rule" to me...
>
> I wrote it from a mathematics background, adding in the fact that the set
> must be named in relational databases where it need not be in mathematics.
> I know it is not always how folks perceive domains, but all it really is is
> just a set that limits the possible values for an attribute, right? Beware
> of anyone who adds in words like "atomic" into definitions of "domain".
> Unless we (as a profession) can find a useful definition of atomic, I'd like
> to leave such useless jargon out of database discussions altogether.

I think the point of the "atomic"/"scalar" arguments is that the usual hacks and kludges in DBMS' to work around the lack of good domain/type support are Evil, Bad, and Wrong.

--
Joe Foster <mailto:jlfoster%40znet.com>  Sign the Check! <http://www.xenu.net/>
WARNING: I cannot be held responsible for the above        They're   coming  to
because  my cats have  apparently  learned to type.        take me away, ha ha!