Re: On formal HAS-A definition

On 12 mei, 00:30, Tegiri Nenashi <tegirinena..._at_gmail.com> wrote:
>
> IMO there is a benchmark formal definition for both HAS-A and IS-A
> already. Both are set theory concepts:
> HAS-A = "element of"
> IS-A = "subset of"
> ...
> I'm not that sure about the HAS-A. Certainly, one can assert that a
> set of attributes has an attribute, but this is quite different from
> saying that a relation has an attribute.

A relation has a body and a heading. So a relation can be viewed as a set of two members, after which your formalism can be made to apply. And a heading is a set of attribute declarations. So under the assumption of "has-a" being transitive, I have indeed made a relation "have an" attribute in the formal sense you spoke of.

I'm just not sure whether such formalism can be made to be of any practical value. Precisely because you can pick any type of set just in order to make the formalism apply.

(PS - second problem, now that I'm on it : what if you disagree with the body-heading view of a relation, and want to insist that a relation _IS_ a set of tuples, i.e. it does _NOT_ "have" a heading in the foregoing sense, but rather the heading that it "has" is just a function of the body (e.g. projecting away the values from each member of the body to retain only the attribute names and the attribute types) ? Then the "having" of something (e.g. an attribute) can also be a consequence of a function being applied to something else (the body). In other words the "having" of something also applies if the "RHS" of your 'element-of' formal concept is in fact any arbitrary function applied to some set (just so long as that arbitrary function yields another set).). Received on Wed May 12 2010 - 02:19:07 CEST