Class servicing

Dear Friends!

I have a following entry in one of the .xinfo files:

////////////////////code/////////////////////////////
 <dependencies>
..........
    <dependency key="SocketManager" 
type="org.apache.avalon.cornerstone.services.sockets.SocketManager"/>
..........
  </dependencies>
////////////////////end of code/////////////////////////////

But the SocketManager is an interface. That is why the expression 
m_socketManager = (SocketManager)serviceManager.lookup( "SocketManager" ); 
doesn´t have sence!

Evidently, serviceManager substitutes SocketManager with some class that 
implements SocketManager interface and returns this class' instance. But I 
can´t find where it is written which class to take instead. 

Could you please give me a hint?

Sincerely 
		Igor