IBM Version 5 manual Discussion, Advantages of using the database

Discussion:

The advantages and disadvantages of establishing relational database relationships in Application Developer:

Advantages of using the database:

￿For application development, relationships between tables are best established in the database. The tables are shared by many applications, and therefore is their common point. When a new application is being developed, the relationship have already being established for the application.

￿The database is a tried and tested product where joins, triggers, indexes, etc. are commonplace. These are the forte of any database. Using a database offers advantages in terms of scalability and performance. This is important especially for large databases.

￿XML documents need to be parsed every time they are accessed and the parsed file must be memory resident during query processing.

Advantages of using the DTD approach in Application Developer

￿This could be the best approach if the relationships between the tables were specific to this application.

￿In e-Business information exchange, DTDs are a common point between different companies intending to share data. Database schemas and database relationships are proprietary to an organization and are used for commercial advantage.This DTD can now be shared between organizations.

￿The shared DTD can be agreed to by the organizations, and then using the XML tools, map parts or all of DTD to the tables in the databases of each organization.

3.The Data Access Definition (DAD) file is then generated. While generating this file, a test harness can also be generated. We will use this to unit test the application until this stage.

4.A new project, the TRAVEL project is created to hold the Web service’s functionality. The project is a J2EE project. As a first step, a Web services configuration group is created. After we have copied the DTD and the DAD into the group, we generate a Data Access Definition eXtention (DADX) file. The resulting file will have to be customized with the parameters for the flight.

5.The DADX file then serves as a base for the construction of our Web services through the Web services wizard. This Web service is based on a Java proxy. The wizard also has the option to generate a Web Services Object Runtime Framework (WORF) run-time component to dynamically generate a test and

Chapter 8. WebSphere and XML approaches 171