Implementing a Provider Proxy 
Web services are primarily used to publish an implemented service already existing in a system so that it can be called by other users (for example, by using a client proxy on the SAP Web AS). However, it is also possible to describe a service interface in WSDL independently of the system, and then implement it later in an application system.
You can use a provider proxy to do the following:
To implement a service that can be addressed by the Integration Server
To implement a service that can be called as a Web service
How the server proxy is used depends on the runtime configuration.
Procedure
Provider proxies are ABAP Objects interfaces. Implement a class for your generated ABAP Objects interface and enter it on the Properties tab page of the provider proxy by calling transaction SE80 or transaction SPROXY. Upon receipt of a message, the ABAP proxy runtime calls the method EXECUTE_SYNCHRONOUS of the implementing class.
Therefore, the application only needs to implement the class for the provider proxy. Proxy generation automatically creates a class with an appropriate signature and empty method. The name of this class is located on the tab page Properties. The application can, however, also enter any class with a suitable signature.
Note
When a message is processed successfully, a commit work is triggered at the receiver.