Re: Smart Database Tricks

On 21 jun, 21:17, vldm10 <vld..._at_yahoo.com> wrote:
>
> On Jun 18, 7:41 pm, Jan Hidders <hidd..._at_gmail.com> wrote:
> >
> > So,
> > since I don't understand your terminology well enough it is simply not
> > possible for me to continue this discussion in a meaningful way.
>
> Before we complete the discussion about the conceptual level I have
> one question.
> Here in example1 I gave the identifier of an entity Car. It is about
> VIN = "vehicle identification number".
> The identifier is not local for Car entity. It is global. Let me say
> we have here global lawful information, which is completely accepted
> as successful solution in the reality and in every country. You state
> that "...adding such artificial implementation concepts are usually a
> bad idea..." Can you explain why VIN is a bad idea?

You misunderstand. There is nothing wrong with VIN if it is a natural concept that was already present in your Universe of Discourse. What I object to is the artificial addition of such concepts if they are not already present. The problem with your definitions is that they are not precise enough to say whether they are or not.

> > If this is a relation then
> > all columns are attributes and since you have represented all the
>
> Can you please, tell me what is the definition of the attribute in RM.

The column of a relation. Conceptually it models a role in the predicate that is associated with the relation.

• Jan Hidders