Hello every, i wrote the code below but seems error happend, and i
don't know why.

var RDFService = Components.classes["@mozilla.org/rdf/rdf-service;
1"].getService(Components.interfaces.nsIRDFService);
var Container = Components.classes["@mozilla.org/rdf/container;
1"].getService(Components.interfaces.nsIRDFContainer) ;
var extensionDS= Components.classes["@mozilla.org/extensions/manager;
1"].getService(Components.interfaces.nsIExtensionMana ger).datasource;

var root = RDFService.GetResource("urn:mozilla:extension:root");
var nameArc = RDFService.GetResource("http://www.mozilla.org/2004/em-
rdf#name");
var toBeUninstalledArc = RDFService.GetResource("http://
www.mozilla.org/2004/em-rdf#toBeUninstalled");

//error here

var init = Container.Init(extensionDS,root);

and the error code is

[Exception... "Component returned failure code: 0x80004005
(NS_ERROR_FAILURE) [nsIRDFContainer.Init]" nsresult: "0x80004005
(NS_ERROR_FAILURE)" location: "JS frame :: chrome://testun/content/test.js
:: anonymous :: line 54" data: no]

can anyone help me?