Is normalization more pratical as a part of a top-down or bottom-up
methodology? WHY?

Hello Helloworld,

Hmm. An interesting question because normalization of a database is
generally considerd a "bottom up" method.

Let's start with a brief definition of top down and bottom up methods.
 Using
  http://courses.mgmt.dal.ca/comm3516/Notes/Notes6.htm
as a reference (near the bottom):

Top down starts by defining the data sets and then define the data
elements within those sets. As a result of this method, you generally
end up with redundant information in one or more tables. Some
references call this Entity - Relationship modeling.

Bottom up starts by defining the required attributes and then grouping
them to form the entities. Another term used for this method is
normalization from functional dependencies.

A good reference that lists a number of attributes of both top down
and bottom up methods is
  http://www.cs.mu.oz.au/~yuan/Ingres/us_13264.html
that also includes an extensive reference list of publications.

Other references and more information can be found at

  http://www.devshed.com/Server_Side/MySQL/Normal/Normal1/print_html
  A good - constructive example of the result of a top-down design and
the normalization of the result.

  http://www.hpdrc.fiu.edu/library/books/datades-book/chapters/chapter5.html
  Skip past the extensive example down to section 5.3 which starts
with a good discussion of normalization - characterizes it as a
"bottom up" method.

  http://www.shef.ac.uk/~rmn/shared/exercise/erd/erd-e2.htm
  http://www.shef.ac.uk/~rmn/shared/exercise/normalis/n-e2.htm
  Two pages that have examples of a simple application and how you
would generally approach them as "top down" vs. "bottom up".

Search phrases included:
  top down database normalization
  bottom up database normalization
  compare "top down" "bottom up" database

So, to answer your original question - normalization is a "bottom up"
methodology and is more "practical" as one. Please note that, a number
of sites also recommend a combination of top down and bottom up
methods when defining your data base.

  --Maniac