[BiO BB] RE: Normalization WAS: database design question

Svensson, B.A.T. (HKG) B.A.T.Svensson at lumc.nl
Tue Mar 2 10:29:23 EST 2004


2nd order tensors calcus in fluid mechanics is also "easy"
once you get used with the concept. However the difference
we talking about here is that tensor calcus is simplifying
the task of understanding the problem, while normalization
theory does not, rather the opposite.

Any student of computer science who has been forced to do
formal deduction with horn clauses know that this is the
most rigorous and silly way to conclude the most trivial
and obvious facts, and as a matter of fact normalization
theory is based on this kind of logical reasoning.



P.S.
Mentioning Barcelona, I just returned from there yesterday
after a visit of four days. It a very fine city, and I were
blessed with a very nice Monday - though the snow last
Sunday was less appreciated. ;)
D.S.


On Tue, 2004-03-02 at 15:29, JRambla wrote:
> Although I'm not sure I understand your comment, normalization must be
> eventually an attitude, an inner practice, essential for a good design
> having a long lifetime. Is like a good laboratory practice, you can obtain
> results without it, but it's a lot more probably to have good results having
> it by default.
> 
> They can look a bit abstract, but when understood they're very practical,
> close to a methodology.
> However, you're right that they're not a checklist, step by step guide.
> 
> Jordi Rambla
> Barcelona (Spain)
> 
> -----Mensaje original-----
> De: bio_bulletin_board-admin at bioinformatics.org
> [mailto:bio_bulletin_board-admin at bioinformatics.org] En nombre de Svensson,
> B.A.T. (HKG)
> Enviado el: martes, 02 de marzo de 2004 14:57
> Para: Bio Bulletin
> Asunto: RE: [BiO BB] RE: Normalization WAS: database design question
> 
> The only problem with (de)normalization theory is that
> it is not that very useful for everyday practical purposes.
> 
> 
> On Tue, 2004-03-02 at 14:21, JRambla wrote:
> > Hi,
> > 
> > According to my experience (near 20 years now) in designing/consulting
> about
> > enterprise databases:
> > 
> > - Normalization is good/desirable in all online systems (like ones where
> > several users can be reading and updating data simultaneously), usually
> > called OLTP systems. Exceptions are not significant at all.
> > - De-normalization is good (indeed mandatory) for datawarehouse & data
> > mining systems where grouping, sorting and summarized data is the real
> > interest. This is due to performance reasons associated to intensive
> > calculations. Also, we will apply de-normalization in history files or
> logs,
> > where you actually need a snapshot of relationships and data in the moment
> > of the entry.
> > 
> > The kind of database I remember starting the thread is a sequence
> database.
> > I will classify it in the first group, although I have little experience
> in
> > that field nowadays.
> > 
> > As I mentioned in the previous e-mail, normalization (usually only the
> > higher levels count as normalized) means not allowing repetitive data to
> > live in the system. I.e. not copying customer address data in every
> invoice
> > in the Invoices table.
> > 
> > That way any change to the data is done only in the "master" record, and
> you
> > don't need to keep track of all places where those data can be copied
> > before. Keeping track of data copies is, usually, a tricky and error prone
> > affair. So, you keep out of it as much as you can.
> > 
> > Opposing to that, using record keys (primary and foreign keys) is good,
> > because you define relationships at database design time, and database
> > engine helps enforcing those relationships when entering data.
> > 
> > Further details or more concrete questions will allow being more specific.
> > 
> > Hope this clarifies a bit more.
> > 
> > Jordi Rambla
> > Barcelona (Spain)
> > 
> > 
> > 
> > -----Mensaje original-----
> > De: bio_bulletin_board-admin at bioinformatics.org
> > [mailto:bio_bulletin_board-admin at bioinformatics.org] En nombre de
> Svensson,
> > B.A.T. (HKG)
> > Enviado el: martes, 02 de marzo de 2004 11:46
> > Para: 'bio_bulletin_board at bioinformatics.org'
> > Asunto: RE: [BiO BB] RE: Normalization WAS: database design question
> > 
> > Thank u for you suggested readings, but I did seek an elaboration on
> > why (high/er?) normalization should be regarded as a good design?
> > 
> > -----Original Message-----
> > From: JRambla
> > To: bio_bulletin_board at bioinformatics.org
> > Sent: 2004-03-02 10:28
> > Subject: RE: [BiO BB] RE: Normalization WAS: database design question
> > 
> > Hi all,
> > 
> > Normalization is a concept that comes from relational database theory,
> > created by the recently deceased Dr.Edgar F. Codd, a mathematician at
> > IBM. That theory is the base of all SQL-whatever world.
> > 
> > Normalization is a group of rules (5, if my memory is right) to apply to
> > table design in order, basically, to eliminate redundancy on data. That
> > redundancy will arise in the form of embarrassing, and sometimes hard to
> > find, consistency problems on data stored in the database.
> > 
> > As was suggested, following those rules is a good starting point to
> > design a database.
> > 
> > You can find a good introduction in
> > 
> > http://www.sequoia.be/consult/method/english.htm
> > 
> > Hope this helps,
> > 
> > Jordi Rambla
> > Barcelona (Spain)
> > 
> > -----Mensaje original-----
> > De: bio_bulletin_board-admin at bioinformatics.org
> > [mailto:bio_bulletin_board-admin at bioinformatics.org] En nombre de
> > Svensson,
> > B.A.T. (HKG)
> > Enviado el: martes, 02 de marzo de 2004 2:13
> > Para: 'bio_bulletin_board at bioinformatics.org '
> > Asunto: [BiO BB] RE: Normalization WAS: database design question
> > 
> > > Normalization is the process of designing a good data model.
> > 
> > Please, explain this statement.
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