Software Architect's Handbook

The bottom-up strategy

The bottom-up approach, in contrast, begins with the web services themselves. They are created on an as-needed basis. Web services are designed and deployed based on immediate needs.

Integration with an existing system is a common motivation for using the bottom-up strategy. Organizations want to add web services to an existing application environment to allow for integration with a legacy system. A wrapper service is created to expose logic in an existing system.

Although this approach is common in the industry, it is not a valid approach to achieving SOA. In order to create a valid SOA later, a lot of effort and refactoring will probably be required. Web services created with this approach may not be enterprise ready ...