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Home -> Community -> Usenet -> comp.databases.theory -> Re: Relation or attribute and why
dawn wrote:
> Bob Badour wrote:
>>David Cressey wrote: >>>dawn wrote: >>>>Gene Wirchenko wrote: >>>>>dawn wrote: >>>>>>Gene Wirchenko wrote: >>>>>>>dawn wrote: >>>>>>>>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." >>>> >>>>Those are high level requirements, but not a conceptual data model. >>>>Conceptual, yes; CDM, no. You need at least an ORM, ERD, or a cleaner >>>>list of propositions related to these requirements, I would think. >> >>David, >> >>If you are going to interract with the self-aggrandizing ignorants, >>please, take the time to point out the most fundamental and profound >>points of their ignorance. Failing to do so only serves to reinforce and >>to spread the widespread ignorance and misconception in our industry.
>>A conceptual model deals with information and not solely data per se. As >>such, the term conceptual data model is ignorant nonsense.
>>The self-aggrandizing ignorant further confuses pretty pictures with >>what they represent. ORM and ERM are diagraming tools one uses to draw >>pretty pictures of conceptual models. (ERD is a diagramming tool to draw >>pretty pictures of logical designs.) The diagrams are not the models any >>more than a tabular picture of a relation alters its degree.
I can see why one would refer to ERD as drawing pretty pictures; nothing wrong with that, BTW - sketches are necessary for any construction beyond the trivial. You have to respect ignorance to be able to see that.
ORM, however, is a different cookie. While it (or rather NIAM, but from what I see of ORM they did not lose NIAM's essence) does have some graphic syntaxes to represent aspects of the model it is a methodic approach to information modeling.
By asking the right people the right questions
about real detailed examples at the right time,
one builds a model from the answers - which as
it happens quite easily translates into a
set of relations in 5NF - including, no
focused on, Date&Darwens external predicates
(see TTM) if you look at it from a RM POV.
The graphics play a minor part.
Like in UML, there is no completeness requirement
for the graphic representation.
Only when some aspect or part is problematic
the graphic representations serve to illustrate
agreements and alternatives on details,
deemed important.
The lack of some graphic features in problematic areas reminds the team that there are still specific questions which are in need of an answer.
To get back on topic - I have never seen the question "Relation or attribute and why" left unanswered after information analysis using NIAM (current incarnation: ORM).
I don't know wether Hugo is reading this - I would
appreciate it if he'ld chime in. He knows a lot more
about ORM than I do. Full disclosure:
I only worked with teams were just some of the
participants were NIAM trained. (I suspect that
Hugo worked in teams were it was the accepted
approach.)
>>>>> Logical gets into the details, but not the implementation. >>>> >>>>A typical use of the term would allow for a conceptual data model to go >>> >>>>from high level to detailed (in the end). [Although if a decision is >>> >>>>made earlier that the requirements have been captured sufficiently to >>>>do flesh it out using common sense in a transition to an LDM, I can >>>>live with some agility.] >> >>See what I mean? Here the self-aggrandizing ignorant once again pretends >>that ignorant nonsense like 'conceptual data model' has meaning.
Dawn, unfortunately I have no advice for you how to deal with the stalker - who BTW appearantly has some nice ignorance about ORM :-) I'll just snip.
> As with any other terms, it has meaning if it is defined. I have
> described such terms before, including in my blog at
> http://www.tincat-group.com/mewsings/2006/01/naked-model.html and
> others have also defined and described them similarly. If your
> definition differs from mine or your term for the same definition
> differs from mine, there is no reason to continue with the name calling
> -- simply explain your terms and definitions if you are not flexible
> enough to expand your glossary or adjust to the language used by
> someone else.
[snip]
>> People who insist that there is only one viable data model tend to >>>nerge the LDM with either the PDM or the CDM. Most of the RM "catholics" in >>>c.d.t. merge the LDM with the CDM, because they think that selecting a data >>>model is a choice with only one answer. >> >>Now, that is just insulting horseshit. Are you projecting your own >>limitations onto others? Or are you just assuming that, because people >>contributing to a theory newsgroup primarily discuss the formalism and >>the theory, they are ignorant of all else? >> >>I find the statement both backhanded and ignorant. It insults all of the >>legitimate contributors here. Shame on you!
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