Re: On formal HAS-A definition
Date: Wed, 12 May 2010 00:53:23 -0700 (PDT)
Message-ID: <4f9cf4cf-c6c9-4760-ba8c-71c7c76f7381_at_l28g2000yqd.googlegroups.com>
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 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.
> 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. Received on Wed May 12 2010 - 09:53:23 CEST