diff --git a/rdf/base/idl/nsIRDFContainer.idl b/rdf/base/idl/nsIRDFContainer.idl
index a19900dad20a..9fc3d112595b 100644
--- a/rdf/base/idl/nsIRDFContainer.idl
+++ b/rdf/base/idl/nsIRDFContainer.idl
@@ -28,26 +28,59 @@ interface nsIRDFContainer : nsISupports {
     readonly attribute nsIRDFDataSource DataSource;
     readonly attribute nsIRDFResource   Resource;
 
-    // Initialize the container wrapper to the specified resource
-    // using the specified datasource for context.
+    /**
+     * Initialize the container wrapper to the specified resource
+     * using the specified datasource for context.
+     */
     void Init(in nsIRDFDataSource aDataSource, in nsIRDFResource aContainer);
 
-    // Return the number of elements in the container. Note that this
-    // may not always be accurate due to aggregation.
+    /**
+     * Return the number of elements in the container. Note that this
+     * may not always be accurate due to aggregation.
+     */
     long GetCount();
 
-    // Return an enumerator that can be used to enumerate the contents
-    // of the container in ascending order.
+    /**
+     * Return an enumerator that can be used to enumerate the contents
+     * of the container in ascending order.
+     */
     nsISimpleEnumerator GetElements();
 
-    // Append an element to the container, assigning it the next
-    // available ordinal.
+    /**
+     * Append an element to the container, assigning it the next
+     * available ordinal.
+     */
     void AppendElement(in nsIRDFNode aElement);
 
-    // Remove the first occurence of the specified element from the
-    // container.
+    /**
+     * Remove the first occurence of the specified element from the
+     * container. If aRenumber is 'true'
+     */
     void RemoveElement(in nsIRDFNode aElement, in boolean aRenumber);
+
+    /**
+     * Insert aElement at the specified index. If aRenumber is 'true', then
+     * the underlying RDF graph will be 're-numbered' to accomodate the new
+     * element.
+     */
     void InsertElementAt(in nsIRDFNode aElement, in long aIndex, in boolean aRenumber);
+
+    /**
+     * Remove the element at the specified index. If aRenumber is 'true', then
+     * the underlying RDF graph will be 're-numbered' to accomodate the new
+     * element.
+     *
+     * @return the element that was removed.
+     */
+    nsIRDFNode RemoveElementAt(in long aIndex, in boolean aRenumber);
+
+    /**
+     * Determine the index of an element in the container.
+     *
+     * @return The index of the specified element in the container. If
+     * the element is not contained in the container, this function
+     * returns '-1'.
+     */
     long IndexOf(in nsIRDFNode aElement);
 };
 
diff --git a/rdf/base/src/nsRDFContainer.cpp b/rdf/base/src/nsRDFContainer.cpp
index 2f1cc18c0297..e6f1da062197 100644
--- a/rdf/base/src/nsRDFContainer.cpp
+++ b/rdf/base/src/nsRDFContainer.cpp
@@ -53,6 +53,7 @@ public:
     NS_IMETHOD AppendElement(nsIRDFNode *aElement);
     NS_IMETHOD RemoveElement(nsIRDFNode *aElement, PRBool aRenumber);
     NS_IMETHOD InsertElementAt(nsIRDFNode *aElement, PRInt32 aIndex, PRBool aRenumber);
+    NS_IMETHOD RemoveElementAt(PRInt32 aIndex, PRBool aRenumber, nsIRDFNode** _retval);
     NS_IMETHOD IndexOf(nsIRDFNode *aElement, PRInt32 *_retval);
 
 private:
@@ -281,6 +282,53 @@ RDFContainerImpl::InsertElementAt(nsIRDFNode *aElement, PRInt32 aIndex, PRBool a
     return NS_OK;
 }
 
+NS_IMETHODIMP
+RDFContainerImpl::RemoveElementAt(PRInt32 aIndex, PRBool aRenumber, nsIRDFNode** _retval)
+{
+    NS_PRECONDITION(_retval != nsnull, "null ptr");
+    if (! _retval)
+        return NS_ERROR_NULL_POINTER;
+
+    *_retval = nsnull;
+
+    if (aIndex< 1)
+        return NS_ERROR_ILLEGAL_VALUE;
+
+    nsresult rv;
+
+    PRInt32 count;
+    rv = GetCount(&count);
+    if (NS_FAILED(rv)) return rv;
+
+    if (aIndex > count)
+        return NS_ERROR_ILLEGAL_VALUE;
+
+    nsCOMPtr<nsIRDFResource> ordinal;
+    rv = gRDFContainerUtils->IndexToOrdinalResource(aIndex, getter_AddRefs(ordinal));
+    if (NS_FAILED(rv)) return rv;
+
+    nsCOMPtr<nsIRDFNode> old;
+    rv = mDataSource->GetTarget(mContainer, ordinal, PR_TRUE, getter_AddRefs(old));
+    if (NS_FAILED(rv)) return rv;
+
+    if (rv == NS_OK) {
+        rv = mDataSource->Unassert(mContainer, ordinal, old);
+        if (NS_FAILED(rv)) return rv;
+
+        if (aRenumber) {
+            // Now slide the rest of the collection backwards to fill in
+            // the gap. This will have the side effect of completely
+            // renumber the container from index to the end.
+            rv = Renumber(aIndex);
+            if (NS_FAILED(rv)) return rv;
+        }
+    }
+
+    *_retval = old;
+    NS_ADDREF(*_retval);
+
+    return NS_OK;
+}
 
 NS_IMETHODIMP
 RDFContainerImpl::IndexOf(nsIRDFNode *aElement, PRInt32 *aIndex)