Re: Objects and Relations

On Feb 16, 9:32 pm, "Marshall" <marshall.spi..._at_gmail.com> wrote:
> On Feb 16, 4:37 pm, "Keith H Duggar" <dug..._at_alum.mit.edu> wrote:
>
>
>
> > I would like to claim that this very discussion reveals one
> > of the advantages of trying to think without entities. It
> > encourages us to think about the /problem/ instead. That is
> > to think about our goals, our requirements, our knowledge,
> > etc. It forces us to consider the facts at hand and those
> > that may arise and design solutions for handling them.
>
> Yeah.
>
> I used to have to deal with this vaguely uneasy
> feeling that terminology was an indicator of some
> piece of wisdom that I didn't have access to.
> So I'd hear talk of, say, UML or OOAD or whatever
> and think, oh, heck, I better learn what that is.
> So I'd buy a book and it'd be really hard to understand.
> I'd push and push, and eventually I'd figure out
> that they were just doing something straightforward,
> like "programming" or "data modelling" or something,
> but they had dressed it up in some fancy clothes,
> added some extraneous concepts, applied some
> arbitrary rules, etc. The intent was to obscure
> rather than to reveal. Make it look like more than
> it was. Really annoying.
>
> I remember reading a guy on comp.lang.functional
> describing going through the same process, but
> over the phrase "dependency injection." After a
> week of reading he figured out it meant "abstraction"
> (as in "lambda abstraction.") In other words it was
> just the process of parameterizing code.
>
> The thing about entities is, what does it buy me?
> I've got relations; I know how they work. Now I'm
> supposed to layer this "entities" concept over the
> top of that. What do I have now that I didn't before?
>
> Seriously, what?
>
> Marshall

I use entities in conceptual modeling. I do not see a need for it in logical modeling, although it is just a level of abstraction away and some products (or standards such as XML) use the term in the logical layer as well. Relations do not fall from the sky, so how did you know what relations to design? You likely looked at nouns/entities/ things at some point, with "entities" being the preferred term (as best I can tell).

I'm in the middle of writing up tips for going from entites and their properties to relations and attributes when working with a non-1NF 2VL DBMS, since there is already plenty written on this in the case that the target DBMS is an SQL-DBMS. If anyone knows of anything written on this subject (the one I'm writing on), please pass along any relevant URLs. I have been highly unsuccessful in finding other writeups  on this.
Thanks --dawn Received on Tue Feb 20 2007 - 21:05:49 CET