Re: Logical Data Model

Matthias Klaey wrote:
> "dawn" <dawnwolthuis_at_gmail.com> wrote:
>
> [...]
>
> >>From Fabian Pascal Papers, FP02, December 2003, Updated February 2005
> >"Un-muddling Modeling" p.13.
>
> hmmm... I am trying to understand these three sentences, and I am
> serious about it. (english is not my first language, so please try to
> be patient with me... :)

No problem. English is my first language and I had to read it several times.

> >"So we have three kinds of models which ought not to be confused.
>
> ok, no problem, jumping ahead: The three models not to be confused
> are
>
> (1) logical model
> (2) conceptual model
> (3) data model

Yes.

>
> > A (1) logical model is the formal representation in the database as seen
> >by users of the (2) conceptual model, the meaning of the database as
> >understood by users; and is the meaning of the database as understood
> >by the DBMS.
>
> Here I am pretty much at a loss. At least it seems to me, that,
> grammatically, the notion of a "database" must have been defined
> *beforehand*.

Somewhere in the paper he states that a database represents a set of axioms.

> I am going to try to separate some parts of this sentence:
>
> (1) "logical model"
>
> seems to be defined as:
>
> (*) "the formal representation in the database as seen by users
> of the conceptual model"
>
> and seems also be defined as:
>
> (**) " the meaning of the database as understood by the DBMS".
>
> Furthermore,
>
> (2) conceptual model
>
> seems to be defined as
>
> (***) "the meaning of the database as understood by users"
>
> >A (3) data model is the formal translation mechanism of
> >the latter to the former."
>
> What is the latter? The (2) conceptual model?
> What is the former? The (1) logical model?
> Thus, trying to rephrase:
>
> (****) "A (3) data model is the formal translation of the
> (2) conceptual model to the (1) logical model."
>
> Is this correct?

That sounds right from my read of it.

> I really do not understand sentences (*), (**), (***), and (****).

>From your rewrite, your understanding of it aligns with mine. Cheers!
--dawn

> With kind regards
> Matthias Kläy
> --
> www.kcc.ch
Received on Fri Oct 27 2006 - 05:28:34 CEST