have defined a Java Interface with the annotation @WebService Compiled the code which went fine

Example:

@WebService
public interface HelloWorldIfc{

Now I tried to define an endpointinterface as 

 @WebService (endpointInterface = "com.ws.HelloWorldIfc")
    public interface HelloWorldIfc{

This compiled fine too

So - should I be defining the endpoint interface on the interface or on implementing class ?
is this attribute of any use - what is its purpose ?
what happens if I dont define it - what do I lose ?
Thanks,
satish

web-services jax-ws
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