Path: utzoo!attcan!uunet!cs.utexas.edu!samsung!brutus.cs.uiuc.edu!psuvax1!psuvm!uh2
From: UH2@psuvm.psu.edu (Lee Sailer)
Newsgroups: comp.object
Subject: Re: I need arguments for OO...
Message-ID: <90043.111559UH2@PSUVM.BITNET>
Date: 12 Feb 90 16:15:59 GMT
References: <1129@swbatl.UUCP> <406@oasis.mrcu> <2954@tukki.jyu.fi>
Organization: Penn State University
Lines: 35

In article <2954@tukki.jyu.fi>, sakkinen@tukki.jyu.fi (Markku Sakkinen) says:
>
>There is a rather new book (1988?) by Shlaer and Mellor, entitled
>"Object-oriented design: modeling the world in data" (may be inexact).
>What it maily teaches is how to make entity-relationship schemata
>and then normalised relational DB schemata out of them. So much for
>object orientation.
>

1.  Those of you who are unfamiliar with logical database design using
diagramming tools such as entity-relationship or logical data modeling
should go look at them.  It is true that a lot of people are simpling
repackaging these techniques, and calling the OO, but they are closely
related to OO, nonetheless.

Some of the classical Structured Analysis people, Coad and Yourdon, for
example, are starting to back pedal a bit with respect to Data Flow
Diagramming.  They note too many cases where analysis goes on forever,
and design never gets off the ground.  Another complaint they have is
that people don't spend enough time on the database model.  I've seen
little clashes where the DBA believes that the logical data model is THE
model, while the SA keeps saying that it is too static and doesn't
show the data flows through the system.  (Add to that people who want to
see the control flows, too.)

Data models *do* show objects, appropriately translated into OOPL in
my opinion.  They focus on the attributes of the objects, and they show
clearly how some real world objects are best decomposed (ie normalized)
into more than one implementation object (ie the relationships among
relations).

They *don't* do a very good job of displaying procedures (ie methods) nor
the messages that objects might send back and forth.

                                                    lee