Here is another memento I wrote to remember the different approaches when writing EJB 3 or Web services.
| TOP DOWN | BOTTOM UP | IN THE MIDDLE | |
| EJB 3 | Develop entity beans first then derive db schema | Develop db schema first and drive upwards to create entity beans from your schema | Create entity beans and db schema and map both respectively |
| Web Services | contract first : in the top-down scenario, the developer first creates or is given the WSDL file for the service, and then must create a component to implement the operations. | First you create a Java bean or EJB bean and then use the Web services wizard to create the WSDL file and Web service. | In this case the starting point consists of both the WSDL file and the implementation component, and the developer must create additional support code that maps between the two. |