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From: cdm@gem-hy.Berkeley.EDU (Dale Cook)
Newsgroups: comp.databases
Subject: Re: ER versus dependency normalization methods.
Message-ID: <1990Dec13.161735.23509@inel.gov>
Date: 13 Dec 90 16:17:35 GMT
References: <34324@netnews.upenn.edu> <1990Dec11.003251.4494@inel.gov> <2370@edat.UUCP> <361@6sigma.UUCP>
Sender: news@inel.gov
Reply-To: cdm@gem-hy.Berkeley.EDU (Dale Cook)
Organization: Idaho National Engineering Laboratory, Idaho Falls, Idaho
Lines: 56

In article <361@6sigma.UUCP>, zuker@6sigma.UUCP (Hunter Zuker) writes:
|> 
|> I can't comment on the generation of 4GL, but real work and decisions
|> have to happen someplace.
|> 

Bingo.  All the CASE tools to date have at best allowed us to concentrate
our efforts where there is a better payoff e.g., analysis.  Many have the
benefit of doing repetitive processes (like Hunter mentions, canonical
synthesis is a great example).  Some actually cause more work and grief,
after factoring in the awful interfaces.  Even the ultimate CASE system
will still require the human specification of data and processes.

I'd like to pose a question to the net.  It seems we have a terminology
gap when we speak of ER diagrams.  My posts have been from the view that
there is a 3 step process in the database design process:

1) Conceptual modeling.  This is what I see as the ER model.  To me, an
   ER diagram rarely contains any more than entities, relationships,
   and cardinalities (1-1, 1-N, N-N, etc).  The ER model includes the
   ER diagram and complete english definitions of the E's and R's.

2) Logical modeling.  This is where I see the introduction of keys and
   attributes.  Many methods exist for doing this; I like bubble charts.
   User views, which include existing file definitions, reports, screens,
   and any paper forms people use, are used to obtain the keys and 
   attributes.  This results in a series of views (bubble charts in the
   method I use) which can then be synthesized into a logical model,
   fully keyed and attributed.

3) The first 2 steps are database independent.  This step is the 
   transformation of the logical model to a physical schema.  It is
   here that I feel physical concerns such as performance should be
   considered (i.e., should I denormalize?).

There is a similar 3 step process in process modeling.  Anyway, my
question is this:  How does this fit in with your development process?
Does your definition of ER diagram contain keys and attributes?

----------------------------------------------------------------------
--- Dale Cook     cdm@inel.gov
"The only stupid question is the unasked one."
The following disclaimer is my employer's.  No flames, please.
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