Index: contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/name/NamespaceStorage.java
===================================================================
--- contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/name/NamespaceStorage.java	(revision 474820)
+++ contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/name/NamespaceStorage.java	(working copy)
@@ -16,6 +16,8 @@
  */
 package org.apache.jackrabbit.jcr2spi.name;
 
+import java.util.Map;
+
 import javax.jcr.NamespaceException;
 import javax.jcr.UnsupportedRepositoryOperationException;
 import javax.jcr.AccessDeniedException;
@@ -26,6 +28,8 @@
  */
 public interface NamespaceStorage {
 
+    public Map getRegisteredNamespaces() throws RepositoryException;
+  
     public void	registerNamespace(String prefix, String uri) throws NamespaceException, UnsupportedRepositoryOperationException, AccessDeniedException, RepositoryException;
 
     public void unregisterNamespace(String uri) throws NamespaceException, UnsupportedRepositoryOperationException, AccessDeniedException, RepositoryException;
Index: contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/name/NamespaceRegistryImpl.java
===================================================================
--- contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/name/NamespaceRegistryImpl.java	(revision 474820)
+++ contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/name/NamespaceRegistryImpl.java	(working copy)
@@ -146,22 +146,26 @@
         // inform storage before mappings are added to maps and propagated to listeners
         storage.registerNamespace(prefix, uri);
 
+        updatePrefixMapping(oldPrefix, prefix, uri);
+    }
+    
+    private void updatePrefixMapping(String oldPrefix, String newPrefix, String uri) {
         // remove old prefix mapping
         if (oldPrefix != null) {
             prefixToURI.remove(oldPrefix);
             uriToPrefix.remove(uri);
         }
         // add new prefix mapping
-        prefixToURI.put(prefix, uri);
-        uriToPrefix.put(uri, prefix);
-
+        prefixToURI.put(newPrefix, uri);
+        uriToPrefix.put(uri, newPrefix);
+  
         // notify listeners
         if (oldPrefix != null) {
             // remapped existing namespace uri to new prefix
-            notifyNamespaceRemapped(oldPrefix, prefix, uri);
+            notifyNamespaceRemapped(oldPrefix, newPrefix, uri);
         } else {
             // added new namespace uri mapped to prefix
-            notifyNamespaceAdded(prefix, uri);
+            notifyNamespaceAdded(newPrefix, uri);
         }
     }
 
@@ -214,8 +218,23 @@
     public String getURI(String prefix) throws NamespaceException {
         String uri = (String) prefixToURI.get(prefix);
         if (uri == null) {
+            try {
+                // try to refresh...
+                Map currentmap = storage.getRegisteredNamespaces();
+                uri = (String)currentmap.get(prefix);
+                if (uri != null) {
+                    updatePrefixMapping(null, prefix, uri);
+                }
+            }
+            catch (RepositoryException ex) {
+              // TODO: log this?
+            }
+        }
+        
+        if (uri == null) {
             throw new NamespaceException(prefix + ": is not a registered namespace prefix.");
         }
+  
         return uri;
     }
 
@@ -224,10 +243,32 @@
      * @see org.apache.jackrabbit.name.NamespaceResolver#getPrefix(String)
      */
     public String getPrefix(String uri) throws NamespaceException {
-        String prefix = (String) uriToPrefix.get(uri);
+        String prefix = (String)uriToPrefix.get(uri);
         if (prefix == null) {
+            try {
+                // try to refresh...
+                Map currentmap = storage.getRegisteredNamespaces();
+                if (currentmap.containsValue(uri)) {
+                    for (Iterator it = currentmap.entrySet().iterator(); it.hasNext() && prefix == null; ) {
+                        Map.Entry entry = (Map.Entry)it.next();
+                        if (uri.equals((String)entry.getValue())) {
+                            prefix = (String)entry.getKey();
+                        }
+                    }
+                    if (prefix != null) {
+                        updatePrefixMapping(null, prefix, uri);
+                    }
+                }
+            }
+            catch (RepositoryException ex) {
+                // TODO: log this?
+            }
+        }
+  
+        if (prefix == null) {
             throw new NamespaceException(uri + ": is not a registered namespace uri.");
         }
+  
         return prefix;
     }
 
Index: contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/WorkspaceManager.java
===================================================================
--- contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/WorkspaceManager.java	(revision 474820)
+++ contrib/spi/jcr2spi/src/main/java/org/apache/jackrabbit/jcr2spi/WorkspaceManager.java	(working copy)
@@ -586,6 +586,13 @@
         service.unregisterNamespace(sessionInfo, uri);
     }
 
+    /**
+     * @inheritDoc
+     */
+    public Map getRegisteredNamespaces() throws RepositoryException {
+        return service.getRegisteredNamespaces(sessionInfo);
+    }
+    
     //----------------------------------------------------< NodetypeStorage >---
     /**
      * @inheritDoc