--- a/devel-versioning.rst	Mon Nov 28 01:32:24 2011 +0200
+++ b/devel-versioning.rst	Mon Nov 28 01:38:54 2011 +0200
@@ -392,10 +392,14 @@
  * New prefix or name in data.
  * List of feature requirements, supported algorighm, etc.
 
-It is essential make code that detect unknown or possibly new format or protocol
-and stop working with them to avoid user data corruption.
+It is essential to make code that detect unknown or possibly new format or
+protocol and stop working with them to avoid user data corruption.
 
-Forward compati
+It is essential to make file format or protocol extensible. This can be achieved
+by:
+
+ * Reserving some possible names/prefixes for future use.
+ * Generalising file format or protocol to envelop more cases.
 
 Reference.
 ==========