Re: How to translate UML Class Diagram into Database Design ?

xtanto_at_hotmail.com wrote:
> Ok,
> May be wrong question..
>
> The question should be :
> Since I am doing OO Application development, I start with Class Diagram
> then I will create ADF Business Component from it the create the
> application with JDeveloper.
> Then I should create Database design for persistence storage, how the
> database design should be to support my application ?
>
> Thank you,
> Krist

You should forget the Class Diagram as you need an ERD that truly supports the data utilization.

What I mean by "data utilization" is that too often developers, especially front-end developers, focus on getting the data into the database as Billy says, treating it like a bit bucket. The truth is that most applications can suffer a bit inserting data as a row can only be inserted one time. Rather the focus should be on the repeated task of extracting and aggregating the data which usually happens multiple times. If it costs me an extra 50 milliseconds to insert a row no one will notice. If it costs me 1 millisecond every time I access a row I have severe pain.

So a relational schema needs to be designed that guarantees data integrity and security while optimizing the eventual usage of the data by report writers. Yes I said REPORT WRITERS. To your front-end application issues are reasonably irrelevant. It is the report writers' input that matters most in the design.

So before you start building tables, etc. define the reports and usages of the data. Then have a very good architect create a design based upon how the data will be utilized. Finally build an object-relational layer that bridges the two using object-relational views or stored procedures.

Unless you have the skills required to determine when it is optimal to use a heap table versus an index-organized table. To determine whether it is optimal to build a B*Tree index versus a bitmap index you should not be writing a single line of DDL.

-- 
Daniel A. Morgan
http://www.psoug.org
damorgan_at_x.washington.edu
(replace x with u to respond)