The Workflow

Business workflows can be invoked from other services or from the presentation components (usually from user process components) using the service interface.
A business workflow invokes other services through a service agent, or directly through the service interfaces. Every outgoing message does not necessarily need to match an incoming message. You can implement service interfaces and service agents in code, or if only simple operations are required, you can use the message transformation.
The Service Agents verifies all outgoing and incoming messages with Policy assertions defined in the policy file which is issued by the Application Manager .The Service Agent is nothing but the Proxy for the Services.