--- a/HACKING.rst	Tue Aug 14 17:31:19 2012 +0300
+++ b/HACKING.rst	Wed Sep 26 23:49:09 2012 +0300
@@ -85,6 +85,18 @@
 
   $ make todo
 
+Dictionary file name convention.
+================================
+
+BNF form::
+
+  FILE ::= PREFIX "-" NAME "-" LANG ".dict-c5"
+  PREFIX ::= "gadict"
+  LANG ::= ISOCODE | ISOCODE "-" ISOCODE
+
+where ``ISOCODE`` is ISO 639-1 language (2 letter) code, currently ``en``,
+``ru``, ``uk`` in use, ``NAME`` is dictionary abbreviated name.
+
 World wide dictionary formats and standards.
 ============================================