Help:how to replace gtk_object_arg_get_info()?

[sandy_21 <sandy_21 sina com>]

I note gtk 2.0  Gtk_Widget_Class_init use
[....]
g_object_class_install_property (gobject_class,
                  PROP_NAME,
                  g_param_spec_string ("name",
                            _("Widget name"),
                           _("The name of the widget"),
                           NULL,
                           G_PARAM_READWRITE));
[....]

but gtk1.2.9 gtk_widget_class_init it like
[...]
gtk_object_add_arg_type ("GtkWidget::name", GTK_TYPE_STRING, 
GTK_ARG_READWRITE, ARG_NAME);
[...]

what's the difference between property and arg?
so the gtk_object_arg_get_info() can't use to judge  whether some object 
has a specific arg,
so how to replace it?
any hits appreciated

Best Regard
Xueqin Chen