diff --git a/ooi/exception.py b/ooi/exception.py
new file mode 100644
index 0000000..5012da5
--- /dev/null
+++ b/ooi/exception.py
@@ -0,0 +1,81 @@
+# -*- coding: utf-8 -*-
+
+# Copyright 2015 Spanish National Research Council
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from oslo_log import log as logging
+import webob.exc
+
+LOG = logging.getLogger(__name__)
+
+
+class ConvertedException(webob.exc.WSGIHTTPException):
+    def __init__(self, code=0, title="", explanation=""):
+        self.code = code
+        self.title = title
+        self.explanation = explanation
+        super(ConvertedException, self).__init__()
+
+
+class OCCIException(Exception):
+    """Base Nova Exception
+
+    To correctly use this class, inherit from it and define
+    a 'msg_fmt' property. That msg_fmt will get printf'd
+    with the keyword arguments provided to the constructor.
+
+    """
+    msg_fmt = "An unknown exception occurred."
+    code = 500
+    headers = {}
+    safe = False
+
+    def __init__(self, message=None, **kwargs):
+        self.kwargs = kwargs
+
+        if 'code' not in self.kwargs:
+            try:
+                self.kwargs['code'] = self.code
+            except AttributeError:
+                pass
+
+        if not message:
+            try:
+                message = self.msg_fmt % kwargs
+
+            except Exception:
+                # kwargs doesn't match a variable in the message
+                # log the issue and the kwargs
+                LOG.exception('Exception in string format operation')
+                for name, value in kwargs.iteritems():
+                    LOG.error("%s: %s" % (name, value))    # noqa
+
+                message = self.msg_fmt
+
+        super(OCCIException, self).__init__(message)
+
+    def format_message(self):
+        # NOTE(mrodden): use the first argument to the python Exception object
+        # which should be our full NovaException message, (see __init__)
+        return self.args[0]
+
+
+class Invalid(OCCIException):
+    msg_fmt = "Unacceptable parameters."
+    code = 400
+
+
+class NotImplemented(OCCIException):
+    msg_fmt = "Action not implemented."
+    code = 501