Re: What is that "more" that makes E-R model truly independent ?

On 24 jul, 03:08, beginner16 <kaja_love..._at_yahoo.com> wrote:
> hello

> I just started learning a little about E-R model. I realize the E-R
> model was created so that we can represent DB at the conceptual level,
> and as such DB is presented independently of the underlying logical
> DB design.

No, we only can represent some aspects of a database with E-R drawings.

> But as I stated before, E-R model diagram would be the same no matter
> if logical DB implementation is hierarchical or relational. For that
> reason I assume that ER modeling is more than just using symbols for
> entity, attributes, relationships

It is not.

>But what is that
> "more" that makes E-R model truly independent of logical DB
> implementation ?

It is more vague and more imprecise. Being even more vague we could be even more independent, and saying nothing we achieve complete independence :-)

For instance this is THE diagram of Alfredo's Universal Data Model:

                 .

Alfredo's Universal Data Model diagram would be the same no matter which system we want to build. Alfredo's Universal Data Model rises independence to unprecedent levels :-)

> 2)
> Does relational model also have its own graphical symbols defined
> ( for graphical representation ) or do we always need "outside"
> diagrams ( E-R model, Bachman's model etc ) in order represent it
> graphically?

No.

Regards
  Alfredo Received on Tue Jul 24 2007 - 05:52:32 CDT