Usage of SingletonService on WLS 9.2

Hi folks.

   I'm trying to deploy a SingletonService on WLS9.2. I've created a POJO which
implements the weblogic.cluster.singleton.SingletonService interface. I've
declared the SingletonService on weblogic-application.xml descriptor, deployed
it, and defined the new SingletonService for my cluster using the Admin console.
When restarting the cluster, the logs show:  <BEA-000187> <The
Singleton Service Throttler is now registered on this server. This server may be
chosen to host this service.>.
   However, I can't see the activate() method being called for any server...
I've put tracing on it, and the method is definetely not being called for any of
the servers in the cluster..  

    First question: would anybody have an idea why the service is not being
activated on any cluster node when the application is started? Do I need to do
something else than creating a class that implements SingletonService interface,
declare it on weblogic-application.xml and also on the admin console for the
cluster I'd like it hosted?

    Second question: how can a client access this service? Does Weblogic has an
API or something for client applications to get an instance of the
SingletonService? or maybe it registers the service on the JNDI tree?  Or it's
up to the service developer to provide a way for the clients to access it?

     thanks very much for your help