Re: Relation or attribute and why

"Gene Wirchenko" <genew_at_ucantrade.com.NOTHERE> wrote in message news:el7772pgbacd9c6melp8qlp6e5iaj1tb1u_at_4ax.com...
> On 23 May 2006 15:44:15 -0700, "dawn" <dawnwolthuis_at_gmail.com> wrote:
>
> >Gene Wirchenko wrote:
> >> On 23 May 2006 13:44:29 -0700, "dawn" <dawnwolthuis_at_gmail.com> wrote:
> >>
> >> [snip]
> >>
> >> >In my example, the conceptual data model includes: name, firstName,
> >> >lastName with relationships such that name has-a firstName and name
> >> >has-a lastName.
> >>
> >> That is part of the logical model. The conceptual model is the
> >> business statement.
> >
> >The identification of name, lastName, firstName and the relationships
> >among these terms is not part of the business scope and definition, the
> >conceptual data model? What would the CDM include related to these
> >terms? I put everything that is conceptual and not directed to a
> >particular implementation model (such as the RM) in the CDM. Where do
> >you draw the (possibly fuzzy) line? --dawn
>
> Possibly fuzzy, but nonetheless.
>
> Conceptual might fit on a napkin: "We want an E-commerce Web site
> for selling our products. It has to be able to handle North America,
> but we plan to go international, so have the capability to add other
> languages, etc. easily without rewriting large chunks. We want
> someone able to complete an order quickly. Do not forget good
> security. OtherCorp recently had a bad situation, and they are taking
> a kicking. Now is our chance, if we do it right."
>
> Logical gets into the details, but not the implementation.
>
> Sincerely,

I disagree.

Conceptual Data Model has enough detail to describe the problem domain from a data centric point of view.
The napkin model doesn't. The difference between the napkin model and the CDM is analysis.

The LDM is the result of design, not analysis. It pertains to the solution domain, not to the problem domain. While the LDM is independent of the specific details of the environment, it's biased towards a particular *class* of implementations. For example, if the LDM uses the relational model, it's biased towards a relational (or SQL) implementation.

If the LDM is inconsistent with the CDM, then either the CDM is wrong, or the requirements have not been met by the LDM.

The PDM adds more design, specific to the platform, volume, traffic, resources, and environment. However, if the PDM is inconsistent with the LDM then there are other problems. Received on Wed May 24 2006 - 14:33:43 CEST