code: private void checkCallService( RequestCallInfo info )
  	{
  		String service = info.request.service;
  		String interfaceChecksum = info.request.interfaceChecksum;
  
  		String key = getServiceKey( info );
  
  		if( usedServices.containsKey( key ) )
  			return;
  
  		ServiceInfo serviceInfo = new ServiceInfo( service, interfaceChecksum );
  		serviceInfo.id = usedServices.size();
  		usedServices.put( key, serviceInfo );
  	}
docs: necessary to be sure that call's service is referenced