diff --git a/uriloader/exthandler/nsHelperAppRDF.h b/uriloader/exthandler/nsHelperAppRDF.h
new file mode 100644
index 00000000000..9e99d9b6a73
--- /dev/null
+++ b/uriloader/exthandler/nsHelperAppRDF.h
@@ -0,0 +1,56 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * The contents of this file are subject to the Netscape Public
+ * License Version 1.1 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of
+ * the License at http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS
+ * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
+ * implied. See the License for the specific language governing
+ * rights and limitations under the License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1999 Netscape Communications Corporation. All
+ * Rights Reserved.
+ *
+ * Contributor(s): 
+ */
+
+// This file holds our vocabulary definition for the helper
+// app data source. The helper app data source contains user specified helper
+// application override information.
+
+
+#define NC_RDF_MIMETYPES				NC_NAMESPACE_URI"MIME-Types"
+// a mime type has the following properties...
+#define NC_RDF_MIMETYPE 				NC_NAMESPACE_URI"MIME-Type"
+#define NC_RDF_DESCRIPTION			NC_NAMESPACE_URI"description"
+#define NC_RDF_VALUE					  NC_NAMESPACE_URI"value"
+#define NC_RDF_EDITABLE   			NC_NAMESPACE_URI"editable"
+#define NC_RDF_LARGEICON				NC_NAMESPACE_URI"largeIcon"
+#define NC_RDF_SMALLICON				NC_NAMESPACE_URI"smallIcon"
+#define NC_RDF_HANDLER				  NC_NAMESPACE_URI"handler"
+#define NC_RDF_FILEEXTENSIONS	  NC_NAMESPACE_URI"fileExtensions"
+#define NC_RDF_CHILD            NC_NAMESPACE_URI"child"
+#define NC_RDF_ROOT 			      "NC:HelperAppRoot"
+#define NC_CONTENT_NODE_PREFIX  "urn:mimetype:"
+#define NC_CONTENT_NODE_HANDLER_PREFIX "urn:mimetype:handler:"
+#define NC_CONTENT_NODE_EXTERNALAPP_PREFIX "urn:mimetype:externalApplication:"
+
+// File Extensions have file extension properties....
+#define NC_RDF_FILEEXTENSION    NC_NAMESPACE_URI"fileExtension"
+
+// handler properties
+#define NC_RDF_SAVETODISK				    NC_NAMESPACE_URI"saveToDisk"
+#define NC_RDF_HANDLEINTERNAL       NC_NAMESPACE_URI"handleInternal"
+#define NC_RDF_ALWAYSASK            NC_NAMESPACE_URI"alwaysAsk"
+#define NC_RDF_EXTERNALAPPLICATION  NC_NAMESPACE_URI"externalApplication"
+
+// external applications properties....
+#define NC_RDF_PRETTYNAME 			    NC_NAMESPACE_URI"prettyName"
+#define NC_RDF_PATH 			          NC_NAMESPACE_URI"path"
+