Re: On formal HAS-A definition

On May 12, 12:53 am, Nilone <rea..._at_gmail.com> wrote:
> On May 12, 12:30 am, Tegiri Nenashi <tegirinena..._at_gmail.com> wrote:
>
> > Again, the IS-A case seems easier because we
> > already have subset relationship defined for each pair of "attribute-
> > compatible" relations.
>
> I consider x IS-A y as a relation named y with a unique constraint on
> x.  Your thoughts?

I'm lost. Example, please?

> > I'm not that sure about the HAS-A.
>
> I consider x HAS-A y as a relation which includes attributes x and y.
> A unique constraint on y denotes aggregation, the lack of it
> association.

Well, I was impressed by Smith&Smith "Aggregation and Generalization" paper a while while ago, but since the rise of UML avoid using these terms. Again, example, please.

> > In addition to that, the
> > algebraic picture [which many of you are aware I'm promoting] tries to
> > demote attributes from being first-class citizens of relational
> > model...
>
> I know you often talk of relational lattices, which I still don't
> comprehend, nor do I understand what you mean here.  I would like to,
> if you care to promote your view to me.

Well, how about "Gentle introduction to relational lattice"? Better yet, you appears to have solid programming background, so I assume downloading http://qbql.googlecode.com/svn/trunk/dist/qbql.jar or even checking in QBQL project in Eclipse wouldn't be a problem? Received on Wed May 12 2010 - 18:26:24 CEST