--- a/devel-versioning.rst	Fri Oct 21 13:48:48 2011 +0300
+++ b/devel-versioning.rst	Fri Oct 21 13:59:08 2011 +0300
@@ -127,6 +127,20 @@
  * Any minor release interchanged starting from some minor.
  * Major release does not interchanged at all.
 
+Product update vs upgrade.
+--------------------------
+
+Product update involve:
+
+ * Replacing product executable files, resources files.
+ * Config files and user data stay unchanged.
+
+Product update involve:
+
+ * Replacing product executable files, resources files.
+ * Config files and used data require modification and performed by upgrade
+   scripts or manually by user.
+
 Release build version data.
 ===========================