- added some details in the README

nova/api/occi/extensions/README

@@ -1,5 +1,25 @@
-# To create extensions:
- 1. define the method to retreive all extension information
- 2. define the extension categories
- 3. define the extension handler(s)
+To create OCCI extensions:
+
+ 1. Define the method to retreive all extension information. This method 
+    **must** have the following signature:
+        def get_extensions()
+    It **must** return a list. That list **must** contain at least one
+    dict. The dict **must** contain a pyssf backend handler. The dict
+    **must** also contain a list of OCCI Categories that are handled by the
+    pyssf backend handler. The OCCI Categories and pyssf backend handler 
+    **should** be defined in the same python file
+
+ 2. Define the extension categories. Depending on your needs you can define
+    Kind, Mixin, Link or Action extensions.
+
+ 3. Define the extension handler(s). 
+
+ Examples of OCCI extensions can be found in the same directory as this README
+ file.
+     fiware.py - this includes a very basic extension
+     occi_future.py - this includes extensions that are considered as future
+                      OCCI-WG extensions 
+     openstack.py - this includes various OpenStack specific extensions
+
+ All extensions are enumerated via __init__.py and loaded via wsgi.py