Re: What is that "more" that makes E-R model truly independent ?
Date: Tue, 24 Jul 2007 18:17:20 +0200
>>> 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.
> What do you mean by "it is not"?
> That E-R modeling is nothing more than just a bunch of symbols or that
> the structure of E-R model does depend on whether underlying logical
> structure is relational or hierarchical ( well isn't the whole point
> of E-R model to be independent, at least for the most part, of
> underlying logical structure ) ?
AFAIK Alfredo does not post riddles, so indeed.
Maybe it helps you to make the distinction between graph and model.
E-R is a group of (mostly kind of sloppy, some with overprecision on unimportant details) modeling languages with a partly graphical syntax.
The graph can only highlight a part of the whole model - that is to say there is no /underlying/ anything, there is just visible and unvisible parts of the model.
>>> 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 :-) >>
> Are Bachman diagrams less vague than E-R diagrams?
Mention your sources for them and we might be able to compare. Received on Tue Jul 24 2007 - 18:17:20 CEST