diff --git a/src/saml2/server.py b/src/saml2/server.py
index b53d6c6..45db33d 100644
--- a/src/saml2/server.py
+++ b/src/saml2/server.py
@@ -86,18 +86,24 @@ class Server(Entity):
             # default database is a shelve database which is OK in some setups
             dbspec = self.config.getattr("subject_data", "idp")
             idb = None
-            if isinstance(dbspec, basestring):
+            if not dbspec:
+                pass
+            elif isinstance(dbspec, basestring):
                 idb = shelve.open(dbspec, writeback=True)
-            else: # database spec is a a 2-tuple (type, address)
-                print >> sys.stderr, "DBSPEC: %s" % dbspec
+            else:  # database spec is a a 2-tuple (type, address)
+                print >> sys.stderr, "DBSPEC: %s" % (dbspec,)
                 (typ, addr) = dbspec
                 if typ == "shelve":
                     idb = shelve.open(addr, writeback=True)
                 elif typ == "memcached":
                     idb = memcache.Client(addr)
-                elif typ == "dict": # in-memory dictionary
+                elif typ == "dict":  # in-memory dictionary
                     idb = addr
-                    
+                elif typ == "mongodb":
+                    from mongodict import MongoDict
+                    idb = MongoDict(host='localhost', port=27017,
+                                    database=addr, collection='store')
+
             if idb is not None:
                 self.ident = IdentDB(idb)
             else:
@@ -150,7 +156,6 @@ class Server(Entity):
         return self._parse_request(xml_string, AttributeQuery,
                                    "attribute_service", binding)
 
-
     def parse_authz_decision_query(self, xml_string, binding):
         """ Parse an attribute query
 
@@ -236,7 +241,8 @@ class Server(Entity):
                 if statement.session_index != session_index:
                     continue
             if requested_context:
-                if not context_match(requested_context, statement.authn_context):
+                if not context_match(requested_context,
+                                     statement.authn_context):
                     continue
             result.append(statement)
 
@@ -286,7 +292,7 @@ class Server(Entity):
                 return self.create_error_response(in_response_to, consumer_url,
                                                   exc, sign_response)
 
-            if authn: # expected to be a 2-tuple class+authority
+            if authn:  # expected to be a 2-tuple class+authority
                 (authn_class, authn_authn) = authn
                 assertion = ast.construct(sp_entity_id, in_response_to,
                                           consumer_url, name_id,
@@ -387,7 +393,6 @@ class Server(Entity):
                 # Just the assertion or the response and the assertion ?
                 to_sign = [(class_name(assertion), assertion.id)]
 
-
             args["assertion"] = assertion
 
         return self._response(in_response_to, destination, status, issuer,
@@ -424,7 +429,8 @@ class Server(Entity):
                 nid_formats = []
                 for _sp in self.metadata[sp_entity_id]["spsso_descriptor"]:
                     if "name_id_format" in _sp:
-                        nid_formats.extend([n["text"] for n in _sp["name_id_format"]])
+                        nid_formats.extend([n["text"] for n in
+                                            _sp["name_id_format"]])
 
                 name_id = self.ident.construct_nameid(userid, policy,
                                                       sp_entity_id,
@@ -438,13 +444,13 @@ class Server(Entity):
                 return ("%s" % response).split("\n")
         
         try:
-            return self._authn_response(in_response_to, # in_response_to
-                                        destination,    # consumer_url
-                                        sp_entity_id,   # sp_entity_id
-                                        identity,       # identity as dictionary
+            return self._authn_response(in_response_to,  # in_response_to
+                                        destination,     # consumer_url
+                                        sp_entity_id,    # sp_entity_id
+                                        identity,        # identity as dictionary
                                         name_id,
-                                        authn=authn,    # Information about the
-                                                        #   authentication
+                                        authn=authn,     # Information about the
+                                                         # authentication
                                         authn_decl=authn_decl,
                                         issuer=issuer,
                                         policy=policy,
@@ -453,7 +459,7 @@ class Server(Entity):
 
         except MissingValue, exc:
             return self.create_error_response(in_response_to, destination,
-                                                  sp_entity_id, exc, name_id)
+                                              sp_entity_id, exc, name_id)
 
     def create_assertion_id_request_response(self, assertion_id, sign=False):
         """