Re: Another view on analysis and ER

On Dec 7, 1:42 am, Jon Heggland <jon.heggl..._at_ntnu.no> wrote:
> Quoth rpost:
>
> > David Cressey wrote:
> >> Bingo! That's the big problem with the literature on ER. Many ER
> >> proponents use ER as if it were a design artifact. I think that 's a
> >> misapplication of the artifact, and I'm pretty sure Peter Chen would agree.
> >> If one is designing a relational system (including but not limited to a
> >> relational database) then using the relational model to capture the design
> >> is a much better idea.
>
> > Well, that reflects what "we" teach: make a model in ER then convert it
> > into a logical relational design. I thought it was how ER is *always* used.
>
> But this conversion is fairly mechanical. Is "design" in this case just
> the little bit of human input that enters this process?
> --
> Jon

For any given conceptual model (assuming in this context that we take the ER model mentioned to be a conceptual model), there are (usually) more than one valid logical designs that will faithfully model it.

The act of choosing among the tradeoffs that those logical models imply, to me, is the act we call designing. I'm unaware of any tools that do this mechanically (at least adequately), so I would say that the human input is more than a "little bit", which you said.

TroyK Received on Fri Dec 07 2007 - 20:21:33 CET