if( log.isDebugEnabled() ) log.debug( "Performed activity for " + state.getName() );
    protected void enterState( State state,                               ProcessContext context )        throws ActivityException, InvalidMotionException    {        Location location = context.getLocation();        location.enterState( state );        Activity activity = state.getActivity();        if( activity == null )        {            return;        }        activity.perform( context );    }