diff --git a/rdf/content/public/nsIRDFContent.h b/rdf/content/public/nsIRDFContent.h
index cca0a108f289..1777a1068aa2 100644
--- a/rdf/content/public/nsIRDFContent.h
+++ b/rdf/content/public/nsIRDFContent.h
@@ -17,6 +17,12 @@
  * Netscape Communications Corporation.  All Rights Reserved.
  */
 
+/*
+
+  An interface for RDF content model elements.
+
+ */
+
 #ifndef nsIRDFContent_h___
 #define nsIRDFContent_h___
 
diff --git a/rdf/content/public/nsIRDFContentSink.h b/rdf/content/public/nsIRDFContentSink.h
index a876d9651139..9d31cc08bc6e 100644
--- a/rdf/content/public/nsIRDFContentSink.h
+++ b/rdf/content/public/nsIRDFContentSink.h
@@ -16,6 +16,14 @@
  * Corporation.  Portions created by Netscape are Copyright (C) 1998
  * Netscape Communications Corporation.  All Rights Reserved.
  */
+
+/*
+
+  An RDF-specific content sink. The content sink is targeted by the
+  parser for building the RDF content model.
+
+ */
+
 #ifndef nsIRDFContentSink_h___
 #define nsIRDFContentSink_h___
 
diff --git a/rdf/content/public/nsIRDFDocument.h b/rdf/content/public/nsIRDFDocument.h
index 6127e8dde0c9..5a458704fb68 100644
--- a/rdf/content/public/nsIRDFDocument.h
+++ b/rdf/content/public/nsIRDFDocument.h
@@ -17,6 +17,14 @@
  * Netscape Communications Corporation.  All Rights Reserved.
  */
 
+/*
+
+  An RDF-specific extension to nsIXMLDocument. Includes methods for
+  setting the root resource of the document content model, a factory
+  method for constructing the children of a node, etc.
+
+ */
+
 #ifndef nsIRDFDocument_h___
 #define nsIRDFDocument_h___