The Model Accelerator is a collection of patterns to support the design of SOA solutions. How these patterns be useful in a J2EE platform?
When we expose a J2EE application as a webservice, how model accelerator will enhance the design?
The Model Accelerator focuses on Business Modeling, Service Specification and Service Identification. Ideally, we've helped you to figure out the right services, ensure that they align with the needs of the business and that they are designed properly. At this point, it becomes an implementation\realization effort. SOA Solutions can be implemented in a number of ways - and one of which that is well supported in the underlying RSA for WebSphere platform is of course J2EE. This all assumes that you are taking more of a top-down approach to creating your solution and the associated services.
If you are started with more of a bottom-up approach, working from an existing set of artifacts we'd take a slightly different tack. The Model Accelerator extends RSA for WebSphere which provides some functionality that comes in handy in this scenario. RSA is able to take existing J2EE artifacts and generate services from them (and can also generate related SoaML model elements). The Model Accelerator comes into play once we have model representations. At this point, the Model Accelerator adds value if we need to further enhance the solution with new services, or further think through the design of the services that we generated.