From 1b920d2045768a4107919eb730627ee3e6df9937 Mon Sep 17 00:00:00 2001
From: dr644w <dr644w@att.com>
Date: Tue, 8 Oct 2013 15:44:17 -0500
Subject: [PATCH] Fixed duplicate creation of namespace prefixes

---
 rdflib/namespace.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/rdflib/namespace.py b/rdflib/namespace.py
index 5d6419e5a..dea7a2dc7 100644
--- a/rdflib/namespace.py
+++ b/rdflib/namespace.py
@@ -351,6 +351,12 @@ def bind(self, prefix, namespace, override=True):
         if prefix is None:
             prefix = ''
         bound_namespace = self.store.namespace(prefix)
+        # Check if the bound_namespace contains a URI
+        # and if so convert it into a URIRef for comparison
+        # This is to prevent duplicate namespaces with the
+        # same URI
+        if bound_namespace:
+            bound_namespace = URIRef(bound_namespace)
         if bound_namespace and bound_namespace != namespace:
             # prefix already in use for different namespace
             #
@@ -361,6 +367,11 @@ def bind(self, prefix, namespace, override=True):
             num = 1
             while 1:
                 new_prefix = "%s%s" % (prefix, num)
+                tnamespace = self.store.namespace(new_prefix)
+                if tnamespace and namespace == URIRef(tnamespace):
+                    # the prefix is already bound to the correct
+                    # namespace
+                    return
                 if not self.store.namespace(new_prefix):
                     break
                 num += 1