The benefits of a Service Oriented Architecture (SOA), which enables organisations to build, deploy and integrate services independent of applications and the computing platforms on which they run may well prove to be one of the most significant architectural innovations for enabling Business - IT integration. The benefits of SOA are broadly of three kinds:
•Business Effectiveness, with the ability to use generic services to build and adapt business applications with agility and greater process efficiency.
•Cost Efficiency, with reduced maintenance costs and skills requirement through platform, technology and location independence.
•Reduced Risk of implementation and support failures because of the ability to deploy incrementally and customise for the needs of each client.
Implementation of SOA can be done in two ways giving tremendous flexibility to both business and information systems chiefs. The Top Down Approach is a more business driven approach where you identify the key business functionalities you may want to provide to your clients, build a business model of the enterprise, defining both processes and semantics, and then mapping this model onto business services. This approach to SOA design ensures better alignment of business and application perspectives. This design approach also ensures separation of the business services from business processes, which may change very frequently.
The top-down SOA approach allows for building a working SOA that supports business initiatives without requiring a major overhaul of existing applications, but it does require a substantial initial investment to define the business model. For more technology savvy companies, the bottoms up approach can be followed originating on the departmental and group level, starting by exposing existing applications as services and building on those services.
The bottom-up SOA design approach usually starts from defining integration services, based on the functionality of existing applications and their integration requirements, which lets us service-enable existing applications and create an integration layer. Services created using this approach are usually tied not to enterprise wide functionality, but to the existing applications, which can create a tight coupling between the application portfolio and business services that might complicate changes in the application portfolio. Although integration services are built using the same technology, they are usually not semantically interoperable. A significant amount of data transformations is required for integration services to work together. Implementation of the business processes in this type of SOA is complex because this approach often leads to embedding the knowledge of the existing application portfolio in high-level processes.
Although the bottom-up approach is easier to implement, it usually delivers less benefit and can be more expensive than the top-down approach. Integration services created in a bottom-up approach might not match business services defined later, thus requiring additional investment in the integration services. Having said that SOA is a new area and even major American corporations who are our clients are feeling their way to success. In the concluding article on this segment, a middle of the road approach will be presented which could lead to less risks and more likelihood of success!
Dr Ganesh Natarajan is Deputy Chairman & MD of Zensar Technologies