PowerDesigner Conceptual modeling/Physical modeling...when to do it

We're trying to understand when in the development life cycle conceptual
modeling should take place. I'm hoping someone on this list can give me some
advice or point me to a good source for this sort of information.

The development process for us appears it should be...
1. Gather business requirements
2. Write a Functional Spec
3. Write a Technical Spec
4. Code

But where in the above 4 steps do we do the DB modeling? Is conceptual in
1&2 and physical in 2&3?

Please advise.


0
Bruce
3/19/2004 1:32:25 PM
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We do conceptual modeling (CDM) during the Business
Requirements Gathering and Function Specifications. In the
transition to Technical Specifications we generate and
modify the Physical Model.

I get a lot of pressure to generate a physical model
earlier, but I put this off as long as possible so I don't
have as much work to do to keep both the CDM and PDM up to
date.

Myron

> We're trying to understand when in the development life
> cycle conceptual modeling should take place. I'm hoping
> someone on this list can give me some advice or point me
> to a good source for this sort of information.
>
> The development process for us appears it should be...
> 1. Gather business requirements
> 2. Write a Functional Spec
> 3. Write a Technical Spec
> 4. Code
>
> But where in the above 4 steps do we do the DB modeling?
> Is conceptual in 1&2 and physical in 2&3?
>
> Please advise.
>
>
0
Myron
3/19/2004 6:39:58 PM
lamb.bruce@mayo.edu wrote...
> We're trying to understand when in the development life cycle conceptual
> modeling should take place. I'm hoping someone on this list can give me some
> advice or point me to a good source for this sort of information.
> 
> The development process for us appears it should be...
> 1. Gather business requirements
> 2. Write a Functional Spec
> 3. Write a Technical Spec
> 4. Code
> 
> But where in the above 4 steps do we do the DB modeling? Is conceptual in
> 1&2 and physical in 2&3?

I rarely use a conceptual model.  It's just easier for me to go straight to a physical 
model and it usually saves time given the compressed nature of my projects.  Most of the 
time my physical model is 95% complete between your steps 1 and 2.  Some tweaking is 
performed during step 3.
-- 
Jim Egan [TeamSybase]
Sybase product enhancement requests:
http://www.isug.com/cgi-bin/ISUG2/submit_enhancement
0
Jim
3/20/2004 12:36:27 AM
Well, Bruce, you have both schools of thought presented.  Excellent!

Myron is doing actual business requirements gathering, as some shops do.  In
this you are not even discussing solutions (technology, databases,
applications, etc) but rather trying to understand exactly what the problem
is.  Gathering data requirements starts with "parsing" business statements
about the processes within the scope of the discussion.  The analyst gathers
data items, entities and relationships at a high level and begins to develop
a structure to store the information to meet the business needs.  After the
business agrees that the data requirements are met by the structure, the
physical model (and sometimes an interim logical model) are produced.  The
physical model is appropriate for discussions with DBAs and developers.  The
logical model is used by architects and other IT groups sometimes, if you
use it at all.

Jim is doing the quick development cycle where there is no line between
defining the problem and designing the solution.  There are advantages and
disadvantages of both approaches.  Myron will spend more time in the earlier
phases of the project, which is frustrating for people who want the solution
faster.  However, the kinds of "tweaking" that Jim might have to do could be
catastrophic if there were serious missing requirements and code was already
written.  The typical issue is a relationship is initially designed as a
simple one-to-many, so a foreign key is added to a table.  Then, in user
testing (end of development!) the user goes, "but what about when there are
2 or more?"  The relationship was really many-to-many, and now the simple
foreign key must be pulled out into an associative table.  This could cause
many hours of work for many people in the project, or even worse a "bandaid
solution" where the business has to deal with the limitations of a system
that wasn't designed properly.  Now, some people (Jim is a very talented
person) can do the proper analysis in their heads and come up with a good
physical model almost right away.  For small shops this works just fine.
With larger shops, the analyst needs to communicate that internal process to
other analysts and business liasons.  They need a more formal procedure, and
higher level models to help in the communication process.

So, it is interesting that both Myron and Jim have distinctly different
approaches, and both can be valid.

Neat.

-- 
Mike Nicewarner [TeamSybase]
http://www.datamodel.org
mike@nospam!datamodel.org
Sybase product enhancement requests:
http://www.isug.com/cgi-bin/ISUG2/submit_enhancement

"Bruce Lamb" <lamb.bruce@mayo.edu> wrote in message
news:405af669$1@forums-1-dub...
> We're trying to understand when in the development life cycle conceptual
> modeling should take place. I'm hoping someone on this list can give me
some
> advice or point me to a good source for this sort of information.
>
> The development process for us appears it should be...
> 1. Gather business requirements
> 2. Write a Functional Spec
> 3. Write a Technical Spec
> 4. Code
>
> But where in the above 4 steps do we do the DB modeling? Is conceptual in
> 1&2 and physical in 2&3?
>
> Please advise.
>
>


0
Mike
3/20/2004 3:18:47 PM
To add to my previous post.  We are in the midst of a
project that involves some very complicated data
requirements.  Part of it involve contracts where the
commodity is priced based on a variety of different methods.
Use the CDM I was able to break out the different types of
pricing using the inheritance features.  The Business
Analysts loved this because they could SEE what attributes
made up each type of pricing method.  "See" being the
operative word.  If I would have shown them the PDM model
that had all the different nullable fields in a single table
they would not have been able to "See" which columns went
with a pricing method.  It simplified their analysis and
made it easier for the people they where working with to
understand the relationships.

> Well, Bruce, you have both schools of thought presented.
> Excellent!
>
> Myron is doing actual business requirements gathering, as
> some shops do.  In this you are not even discussing
> solutions (technology, databases, applications, etc) but
> rather trying to understand exactly what the problem is.
> Gathering data requirements starts with "parsing" business
> statements about the processes within the scope of the
> discussion.  The analyst gathers data items, entities and
> relationships at a high level and begins to develop a
> structure to store the information to meet the business
> needs.  After the business agrees that the data
> requirements are met by the structure, the physical model
> (and sometimes an interim logical model) are produced.
> The physical model is appropriate for discussions with
> DBAs and developers.  The logical model is used by
> architects and other IT groups sometimes, if you use it at
> all.
>
> Jim is doing the quick development cycle where there is no
> line between defining the problem and designing the
> solution.  There are advantages and disadvantages of both
> approaches.  Myron will spend more time in the earlier
> phases of the project, which is frustrating for people who
> want the solution faster.  However, the kinds of
> "tweaking" that Jim might have to do could be catastrophic
> if there were serious missing requirements and code was
> already written.  The typical issue is a relationship is
> initially designed as a simple one-to-many, so a foreign
> key is added to a table.  Then, in user testing (end of
> development!) the user goes, "but what about when there
> are 2 or more?"  The relationship was really many-to-many,
> and now the simple foreign key must be pulled out into an
> associative table.  This could cause many hours of work
> for many people in the project, or even worse a "bandaid
> solution" where the business has to deal with the
> limitations of a system that wasn't designed properly.
> Now, some people (Jim is a very talented person) can do
> the proper analysis in their heads and come up with a good
> physical model almost right away.  For small shops this
> works just fine. With larger shops, the analyst needs to
> communicate that internal process to other analysts and
> business liasons.  They need a more formal procedure, and
> higher level models to help in the communication process.
>
> So, it is interesting that both Myron and Jim have
> distinctly different approaches, and both can be valid.
>
> Neat.
>
> --
> Mike Nicewarner [TeamSybase]
> http://www.datamodel.org
> mike@nospam!datamodel.org
> Sybase product enhancement requests:
> http://www.isug.com/cgi-bin/ISUG2/submit_enhancement
>
> "Bruce Lamb" <lamb.bruce@mayo.edu> wrote in message
> news:405af669$1@forums-1-dub...
> > We're trying to understand when in the development life
> > cycle conceptual modeling should take place. I'm hoping
> someone on this list can give me some
> > advice or point me to a good source for this sort of
> information. >
> > The development process for us appears it should be...
> > 1. Gather business requirements
> > 2. Write a Functional Spec
> > 3. Write a Technical Spec
> > 4. Code
> >
> > But where in the above 4 steps do we do the DB modeling?
> > Is conceptual in 1&2 and physical in 2&3?
> >
> > Please advise.
> >
> >
>
>
0
Myron
3/22/2004 6:51:44 PM
I appreciate all the opinions. They are very helpful.
Sincerely,
Bruce

<Myron> wrote in message news:405f35c0.278a.846930886@sybase.com...
> To add to my previous post.  We are in the midst of a
> project that involves some very complicated data
> requirements.  Part of it involve contracts where the
> commodity is priced based on a variety of different methods.
> Use the CDM I was able to break out the different types of
> pricing using the inheritance features.  The Business
> Analysts loved this because they could SEE what attributes
> made up each type of pricing method.  "See" being the
> operative word.  If I would have shown them the PDM model
> that had all the different nullable fields in a single table
> they would not have been able to "See" which columns went
> with a pricing method.  It simplified their analysis and
> made it easier for the people they where working with to
> understand the relationships.
>
> > Well, Bruce, you have both schools of thought presented.
> > Excellent!
> >
> > Myron is doing actual business requirements gathering, as
> > some shops do.  In this you are not even discussing
> > solutions (technology, databases, applications, etc) but
> > rather trying to understand exactly what the problem is.
> > Gathering data requirements starts with "parsing" business
> > statements about the processes within the scope of the
> > discussion.  The analyst gathers data items, entities and
> > relationships at a high level and begins to develop a
> > structure to store the information to meet the business
> > needs.  After the business agrees that the data
> > requirements are met by the structure, the physical model
> > (and sometimes an interim logical model) are produced.
> > The physical model is appropriate for discussions with
> > DBAs and developers.  The logical model is used by
> > architects and other IT groups sometimes, if you use it at
> > all.
> >
> > Jim is doing the quick development cycle where there is no
> > line between defining the problem and designing the
> > solution.  There are advantages and disadvantages of both
> > approaches.  Myron will spend more time in the earlier
> > phases of the project, which is frustrating for people who
> > want the solution faster.  However, the kinds of
> > "tweaking" that Jim might have to do could be catastrophic
> > if there were serious missing requirements and code was
> > already written.  The typical issue is a relationship is
> > initially designed as a simple one-to-many, so a foreign
> > key is added to a table.  Then, in user testing (end of
> > development!) the user goes, "but what about when there
> > are 2 or more?"  The relationship was really many-to-many,
> > and now the simple foreign key must be pulled out into an
> > associative table.  This could cause many hours of work
> > for many people in the project, or even worse a "bandaid
> > solution" where the business has to deal with the
> > limitations of a system that wasn't designed properly.
> > Now, some people (Jim is a very talented person) can do
> > the proper analysis in their heads and come up with a good
> > physical model almost right away.  For small shops this
> > works just fine. With larger shops, the analyst needs to
> > communicate that internal process to other analysts and
> > business liasons.  They need a more formal procedure, and
> > higher level models to help in the communication process.
> >
> > So, it is interesting that both Myron and Jim have
> > distinctly different approaches, and both can be valid.
> >
> > Neat.
> >
> > --
> > Mike Nicewarner [TeamSybase]
> > http://www.datamodel.org
> > mike@nospam!datamodel.org
> > Sybase product enhancement requests:
> > http://www.isug.com/cgi-bin/ISUG2/submit_enhancement
> >
> > "Bruce Lamb" <lamb.bruce@mayo.edu> wrote in message
> > news:405af669$1@forums-1-dub...
> > > We're trying to understand when in the development life
> > > cycle conceptual modeling should take place. I'm hoping
> > someone on this list can give me some
> > > advice or point me to a good source for this sort of
> > information. >
> > > The development process for us appears it should be...
> > > 1. Gather business requirements
> > > 2. Write a Functional Spec
> > > 3. Write a Technical Spec
> > > 4. Code
> > >
> > > But where in the above 4 steps do we do the DB modeling?
> > > Is conceptual in 1&2 and physical in 2&3?
> > >
> > > Please advise.
> > >
> > >
> >
> >


0
Bruce
3/23/2004 1:39:52 PM
Reply:

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