Design, Implement, and Test Any Necessary Databases

Most systems have a database, and you need to understand how persistent data is to be stored in, and retrieved from, the database. A first assumption is to have a database table for each persistent design class, with a column for each attribute containing persistent data. This provides a very simplified, first-draft logical database.

If you are using relational databases and doing object-oriented development, you need to pay special attention to when and how persistent data shall be retrieved from the database and placed into instantiated objects, and how to design the physical database to achieve required performance. Using an object-oriented database makes the mapping easier by automating a lot of the logics involved.

During Elaboration, you want to decide how to handle persistency in your system, and then design, implement, and test one or several architectural mechanisms that can be reused for persistency issues. Also establish the major database structures (tables, indexes, and primary and foreign key columns ) to support the architecturally significant scenarios. In addition, representative data volumes should be loaded into the databases to support architectural performance testing. Based on the results of performance testing, the data model may need to be optimized, including but not limited to denormalization, optimizing physical storage attributes or distribution, or indexing.

In Construction, additional columns may be added to tables, views may be created to support query and reporting requirements, and indexes may be created to optimize performance, but major restructuring of tables should not occur. This would be a sign that the architecture was not stable and that Construction was started prematurely, or that you have evolving requirements that add architectural risks to the project.

You can find comprehensive guidance within the Rational Unified Process in the area of database design (see the activity Database Design and the Guidelines: Data Model). You'll also find useful information in Ambler 2000.